Well, keep in mind that the only time he fought at 144, he did so against Floyd Mayweather- which means something.
You had two counterpunchers in the ring, one at his normal weight class and the other 9 lbs. higher (actually more because May came in 2 lbs. overweight), Mayweather had a longer reach, was more crisp, and was the much larger fighter overall- and Marquez still landed some shots on him.
Put him back down to his division against guys the same size- Diaz, Katsidis and the like- and he absolutely destroyed them. Both were come forward fighters that Marquez did what he always does- took some shots early, then totally picked them apart with devastating punching down the stretch.
Marquez has already done this EXACT thing to Pacquaio- TWICE. Pac is going to come forward, and get hit, and he's gonna wanna fight like he always does, and Marquez is gonna counter the fuck out of him.
No matter what, it's a terrible stylistic matchup for Pac - a cerebral counterpuncher who has power.
Like I said, I'm holding off until I see the tune up, but damn, Marquez beat this kid twice, he'll do it once more.