By TMZ Sports

The guy Mickey Rourke knocked out last month in Russia is now admitting what everyone with eyes has suspected all along -- the whole match was a total SHAM.

62-year-old Rourke made headlines for the KO against 29-year-old Seymour because it looked so much like a fix. As we told you ... Seymour initially denied any hijinx, but over the weekend in L.A. he came clean.

You gotta watch him describe the alleged set up -- he claims almost all his punches were choreographed. As for why he's spilling his guts now ... Seymour says the pressure to keep lying was getting to him -- and he's angry Rourke's people "dragged their feet"  on paying up.

So, was Mickey in on the fix? Seymour's got a strong opinion on that.

Rourke's trainer still denies the fix, and tells us he believes Seymour will change his story to whatever he thinks will make him more money.