When he was aged 3, Antonio Carlos Silva observed a karate demonstration at a playground, which stirred his interest in the martial arts, and later lead to him being one of the most agile heavyweights in Mixed Martial Arts. Silva trained in karate for 13 years before transitioning to Jiu Jitsu in his native Brazil. In 2005, Silva trained with the famed Wolfslair MMA Academy which lead to his first professional mixed martial arts bout when he fought in UK Mixed Martial Arts Championship. Silva used his greater size to control his opponent, Tengiz Tedoradze, while clinching early in the stand up. Silva took Tedoradze to the ground and landed several unanswered strikes to his dazed opponent which ended the fight by technical knockout just over a minute in the bout.Silva fought Marcus Tchinda in another UK promotion, Cage Warriors Fighting Championship. Silva defeated Tchinda by submitting him with punches. Silva had his first championship opportunity when he fought at Cage Rage 12 for the Cage Rage Heavyweight title against Rafael Carino. Carino held Silva against the cage until the referee pulled them apart. Silva hit Carino with a right hook which echoed, and Carino forced him against the fence again. Silva fought his way to reverse Carino and hold him against the cage. When Carino ran from his opponent's grasp against the cage, Silva hit him with punches which sent him to the ground. Silva went to the ground and landed punches on the unresponsive Carino which lead to a fight stoppage just short of 3 minutes. Silva won a second title when he fought Ruben Villareal at "Strike Force 4" for the vacant Cage Warriors Fighting Championship's Super-heavyweight title. Villareal attacked first with legs kicks and Silva reacted with leg kicks and punches. Silva used his size advantage in grasping Villareal's body against the cage then taking him to the ground. Silva attacked Villareal with punches from top position. Silva then pushed him against the fence to continue the attacks with knees, punches, and hammer-fists until the referee stopped the bout over 3 minutes into the fight. Silva's victory unified the Cage Rage and Cage Warriors championships. Silva defended the Cage Warriors Super-Heavyweight World Title when he fought Tadas Rimkevicius on the "Strike Force 5" card. Soon after missing a head kick, Silva ran and got a double-leg take-down of Rimkevicius against the fence. He proceeded to landed a barrage of punches in between his opponent holding his head. The bout ended after a series of left hammer-fists and punches resulted in a referee stoppage by way of TKO. Silva left Cage Warriors and fought Tom Erikson in Japan for K-1 Hero's 5. Erikson landed the first strike by way of a push jab. Silva forced him against the ropes and hit him with knees and body punches. The referee separated them and Erikson went on the offense and hit Silva with punches. Silva moved forward with a double-leg take-down on Erikson. From top position he hit his opponent with punches and hammer-fists until the referee stopped the fight. Silva's next fought Georgy Kaysinov at K-1 Hero's 7 and defeated his opponent by technical knockout short of three minutes in the first round. Silva fought Eric Pele in Canada for a super-heavyweight bout on the December 2006 BodogFight: USA vs. Russia (2006) card. Silva stalked Pele and landed two hard right kicks. Silva backed Pele into a corner of the ring and unleashed punches which caused Pele to cover up. Pele escaped the corner and fell from a knee and punches from Silva, which sent part of his body through the ropes as Silva attacked him on the ground. The referee intervened and allowed Pele to be inside the ring completely, then resume the bout with both fighters standing up. Silva landed a hard right kick which made contact with Pele's groin and the referee stopped the action to allow Pele to recover. Silva again went on the offensive with punches and Pele landed a few of his own. Silva again resumed the pressure with knees and punches as Pele covered up. Pele hit Silva with a massive right punch causing him to fall to the ground. From the ground Silva fought to recover as Pele landed more punches to his head and the referee stopped the fight. An upset Silva and his corner team questioned the referee's decision to stop the fight. Silva was signed in Elite XC (2007) (Elite Xtreme Combat) and fought Wesley 'Cabbage' Correira at super-heavyweight on the card at Elite XC: Destiny (2007). They exchanged hard punches until "Bigfoot" got the advantage by pulling Correira's legs from underneath him, then ended up on top to land strikes. Silva allowed Correira to stand, while holding his neck in a choke position and delivering right knees to the head. Correira survived and averted a second take-down by Silva. The action ended up against the fence and the fighters were separated. Silva connected a jumping right knee to Correira's face, which hurt him, then continued with punches to the ground. "Cabbage" covered up and the referee stopped the bout. Silva made the limits of the heavyweight division to fight Jonathan Wiezorek at Elite XC: Renegade (2007). Silva avoided Wiezorek when he rushed towards him on the cage and hit him with strikes. Wiezorek again threw punches to work his way into a clinch, and Silva pushed him away. Silva landed a knee then a leg kick to his opponent. A third rush by Wiezorek near the cage was met with strikes from Silva. Wiezorek was stunned by the punches and attempted to take Silva to the ground. Silva sprawled and controlled Wiezorek from top. Silva landed punches and elbows from half-guard. Silva fought to full mount and landed more strikes to his opponent on the ground. Wiezorek moved his body around to avoid the brunt of the strikes, until Silva secured his opponent's back and obtained the rear-naked choke submission. "Bigfoot" moved down to heavyweight for matches against Gary Turner and Shane Carwin, neither of which materialized. A third opponent was founded in UFC heavyweight champion Ricco Rodriguez at Elite XC: Street Certified (2008). It became Silva's first bout to make it through all rounds, and he got the win over Rodriguez by split decision. To inaugurate an EliteXC's heavyweight champion, Silva fought Justin Eilers at EliteXC Saturday Night Fights: Episode #1.2 (2008)("Unfinished Business"). Silva landed a leg kick and Eilers circled around him on the outside the middle of the cage. They exchanged a few strikes until Silva ran forward and grabbed Eilers' legs to ground him. Silva leaned his weight on Eilers' back and hit with punches, a knee to the body, and more punches. Referee Herb Dean intervened to deduct a point from Silva due to illegally striking Eilers on the back of his head. The fight resumed and Silva connected with kicks to the head and leg. His punches forced Eilers backward and then a lost of balance to the ground. Silva tried to capitalized on his downed opponent but Eilers stood up. Silva pushed him against the cage and hit him with punches to the face and knees to the leg. The bout went off the cage and both fighters exchanged punches until round's end. In round two, Silva was punched by Eilers and counterstrike to send Eilers back into the cage. Silva struck with a knee and hit Eilers with a barrage of punches. Eilers turned his back and held on the cage then collapsed to his knees. Silva continued punching until the bout was stopped, earning him EliteXC's heavyweight championship. In August 2008, the California State Athletic Commission (CSAC), which sanctioned "Unfinished Business" (EliteXC Saturday Night Fights: Episode #1.2 (2008)), released urinalysis results which indicated Silva had tested positive for a banned anabolic agent commonly used by veterinarians: Boldenone. Silva and his management contested the results, citing his suffering of acromegaly--the cause of his massive body--and the fact that he had surgery in 2007 to remove a brain tumor. Silva had his team file a lawsuit against the CSAC suspension, while EliteXC's management decided keep the title on him until the situation was resolved. Elite XC (2007) ended operations in October 2008, the same month the CSAC upheld Silva's suspension accompanied with a $2,500 fine. These factors prevented Silva from ever defending the title, making him the first and only holder of the EliteXC heavyweight championship. With his management citing issues with the CSAC test results and financial needs, Silva fought in Japan. Silva fought Yoshihiro Nakao at "No Ran 2009" for Japan's Sengoku promotion. Nakao landed an early left punch to Silva's body then a right hook to the head. A right front kick by Silva landed, then a right kick was blocked by Nakao. Nakao's left kick was blocked, then Silva punches him in the face twice. Nakao quickly ran for a take-down, and was met by a sprawl by Silva. Silva landed a legal knee to his downed opponent and landed punches. Nakao stood up from Silva's control, and became the recipient of a flying knee. Silva's landed a left body kick left then a grazing left leg kick to Nakao's right leg. Silva landed two more punches before Nakao ran away, slowed down, and indicated for a time out from the referee. Silva won via technical knockout due to Nakao's left knee injury. In early September 2009, almost two months after the CSAC suspension expired, Silva again fought for Sengoku, submitting Jim York in the first round. When Silva returned to fight in the United States, no action was taken to prevent him from fighting for Strikeforce (2006). Silva fought on the CBS Strikeforce M-1 Global Saturday Night Fights (2009) card. Silva initially had the advantage in the first round, getting the better of the striking and hurting Werdum. Werdum recovered then rebounded in the second and third rounds, getting Silva on the ground then landing punches, and pushing him against the fence. Silva loss to Werdum by unanimous decision. Silva's second bout in the promotion happened with Andrei Arlovski at Strikeforce M-1 Global: Fedor vs. Werdum (2010). Silva was dominant in round one by hurting Arlovski with punches, getting him on the ground and against the cage. Arlovski was more aggressive in the second round by exchanging with strikes and clinching with Silva. Silva and Arlovski continued clinching and striking in the third round, until Silva slammed his opponent to the ground and control the action for the rest of the fight. Silva won unanimously on the judges scorecards. At Strikeforce: Henderson vs. Babalu 2 (2010), Silva's scheduled opponent was to have been Valentijn Overeem, however an elbow injury forced him from the bout. King Of The Cage light-heavyweight champion, Mike Kyle, was brought in as a replacement.Kyle landed powerful punches to Silva's head early in the first round with two jabs and a big right punch, sending Silva to the ground, and on the verge of a victory. Kyle went to the ground and landed punches and hammer fists as Silva covered up a for short time then pulled guard and used his hands to control Kyle from the bottom. Silva recovered to make it to the second round where he hit Kyle with a massive right punch and took him down to the ground. Silva applied a Darce choke and Kyle did not submit to then escaped fro. Silva returned to full mount and resumed the ground and pound attack from top to earn a technical knockout win. Silva became a participant in the Strikeforce World Grand Prix Heavyweight Tournament. He was matched up against Fedor Emelianenko at Strikeforce: Fedor vs. Silva (2011), in the main bout of the event which commenced the tournament. Silva placed Fedor on the defensive early, hitting him with a left low kick, hard punches, then used his giant frame to hold Emelianenko against the fence. Fedor attempted a guillotine choke which Silva countered by hoisting his opponent up and falling to the ground. Fedor ended up on top and land punches until Silva stood up. Silva hit Fedor with more punches and took him to the ground just before rounded one ended. Silva quickly took Emelianenko down in the second round and bloodied him with enormous punches. Fedor alternated between his stomach and back to avoid the massive strikes of "Big Foot". Silva applied a rear-naked choke which Emelianenko survived. Silva then transitioned to an arm-triangle choke submission on his opponent's right side. Emelianenko did not submit, and escaped from the hold while Silva retained his dominant position on top. He tried another submission by grabbing Emelianenko's right leg for a knee-bar. Fedor fought out of it and applied a leg-lock to Silva's right leg until the round expired. Before the third round could begin, the cage side physician ceased the bout due to Fedor's right eye, which was swollen shut. Silva advanced to the semifinals of the tournament by way of a technical knockout victory.