Floyd Mayweather started slowly, but came on strong in the middle rounds and defeated UFC star Conor McGregor with a 10-round TKO. Referee Robert Byrd stops it at 1:05 of the 10th round as McGregor was completely gassed and Mayweather took advantage. Mayweather, 40, improved his record to 50-0 to surpass Rocky Marciano's mark of 49-0.

Here's a round-by-round update of the highly anticipated fight.

Round 1: They come out with Mac on the attack. May being defensive, Left by Mac misses. Mac goes for the body, Not much action here. Mac does some hot-dogging with hands behind his back. Floyd throws first jab. 30 punches by Mac and catches May with a counter left uppercut. Floyd looks to be waiting for Mac to punch himself out. First round to Mac.

Round 2: Mac has him in the corner and Mac throws a hammer fist and Byrd stops it. May connects. In the middle of the ring. Little movement from May. Mac switches stances and connects. Mac throws combo. May doing little work. Mac goes to the body with a left. Mac jabbing. He roughs up May. Mac grabs May around the waist and throws a punch. Another round for McGregor. 2-0.

Round 3: Mac gets him in the corner and throws a hammerfist punch again on top of the head. More puncing on top of the head. Mac fighting dirty. Mac throws a left and misses. May lunges in. This is kind of awkward. Left uppercut by May, then scores with two jabs. May connects with a right. Mac switches stances while throwing. Again, Mac hits on top of the head. Mayweather starting to move and throw more. But another Mcgregor round 3-0.

Round 4: Mac gets May on the ropes and attacks. May doesn;t look like his old self. Left by Mac but May counters with a right. Another right. May trying to get on the inside. May combo, and Mac throws some jabs. Counter left by Mac scores. Mac hits on top of the head again. Left uppercut lands. May having trouble getting punches off. This is a very slow start by May. Another close round by I give it to Mac. 4-0.

Round 5: Mac breathing hard but still looking good. May can't seem to get his punches off. The awkwardness seems to puzzle him. May lands a left. Right by May then he shoves Mac at the end of the round and is scolded by Byrd. Close round again. I have Floyd taking his first round, but very close. 4-1.

Round 6: May goes to the body with a right. Floyd throws =an overhand right and he's starting May gets a combination but Mac counters with a left hand. Mac sticks his tongue out. Floyd puts his head down but comes back to land another right. He' starting to assert himself. Good round for Floyd. 4-2 Mac.

Round 7: This is where you expect Mac to start to get gassed. Not a lot on his punches right now. Neither fighter is throwing bombs. May right hand scores. Another lead right by May lands. Two more rights by May. He's finding the target. Another one followed by a job. This is not the Mac that Jose Aldo remembers. May has a good round. 4-3 Mac.

Round 8: Mac hits on top of the head. May turns around. Mac acquitting himself well. May starting to walk Mac back. Fighters in a clinch. Mac fighting with his mouth open. Left to the body by Mac. Left uppercut by May. Combo by Mac lands nicely. Very close round. Could go either way but I give it to Mayweather to tie it up.

Round 9: Mac comes out and throws a body shot that might have hurt May, then is warned by Byrd. May comes forward and attacks, then lands with a big right. Right hand by May to the face lands. They clinch again. You can see Mac gassed as Mayweather goes after him. Mac is holding on to stay up. Mac looks like he;s ready to drop and holds May. May attacks, this is alsomost a 10-8 round, but now quite. McGregor can barely move from fatigue. Big round for May. 5-4 Mayweather.

Round 10: Mac really looks fatigued as he has gone farther than he ever has in a UFC fight. Floyd has McGreg or on the ropes and Robert Byrd stops it. Floyd wins by TKO in the 10th. Great comeback after a slow start.