I was going to state the same as of this point it would be Sergio, but lets see how far Tim can take it.
Going to make an unpopular choice and say Tim by close UD. If this is a fight at 154, then that's the version of Martinez we use. I don't know if was the weight or what, but 154 Martinez was not as good as he was at 160. At jrMW, his best win was a MD over Kermit Cintron. He then lost to Paul Williams before moving up. You'll see most of his wins at 154 and lower were against very meager comp. At 160, no doubts Sergio wins. But at 154, would probably go with TT.
Timmy is still improving as a fighter, no way he beats Martinez at 154. Martinez was too fast, too slick.
He barely got by Kermit Cintron at 154, which was Cintron's first bout at 154. And Cintron got in to boxing late himself, didn't do much well but had a punch. He was like a lesser Keith Thurman. Martinez sure wasn't too slick for the limited 'Killer'. Martinez, at his best at 154, didn't really do much there. Just mostly beat guys w/ terrible records. I know the obvious answer is Martinez, but due to his late run at MW.
I'm not sold on Tyszu rn. He's getting better every fight but he's shown me nothing to suggest he'd beat Martinez in a hypothetical matchup.
I recall Sergio Martínez beating Cintron clearly and then being robbed twice in one fight against him. First robbed of a KO win, and then robbed of a clear decision win. Martinez didn’t do much at 154 other than fight no names but he did look pretty impressive against Alex Bunema.
Was a weird fight. Can't say I saw the headbutt Cintron complained about. But IMO, Sergio should have beaten Kermit by a WIDE margin just based on talent alone.