UFC San Antonio: 'The Big Ticket' Walt Harris stops Aleksei Oleinik in 12 seconds (VIDEO)

UFC heavyweight contender Walt "The Big Ticket" Harris scored the biggest, most impressive win of his UFC career at UFC San Antonio on Saturday as he knocked out Russian submission ace Aleksei Oleinik in just 12 seconds.

Harris was returning to action after serving a USADA anti-doping suspension after unknowingly ingesting a tainted supplement, and the American was clearly keen to make up for lost time against the dangerous Oleinik, whose submission threat has seen him rack up an astonishing 45 submission wins from his 71 career fights.

But the Russian was given no opportunity to implement his lethal grappling game as Harris launched into the action from the very start of the contest.

After throwing a couple of quick jabs, "The Big Ticket" launched into a flying knee attempt, which missed its target and caught the outside of Oleinik's shoulder.

However, Harris' follow-up left hand certainly didn't miss, as he found his mark with a huge shot that sent his opponent crashing to the canvas as referee Dan Miragliotta dived in to stop the contest after just 12 seconds.

It gave Harris a much-needed comeback win, and the third-fastest heavyweight KO in UFC history.

And with the 36-year-old keen to get back into the cage at UFC 242 in Abu Dhabi, or the UFC Fight Night event in Vancouver the following week, Harris said matchmaker Mick Maynard simply had to find him an opponent and he'd sign the contract.

After a performance like that, the queue of contenders happy to face him is likely to be a very short one.