Hard to say because Thurman just struggled. I think Thurman could be on the way down. It sounds crazy that the younger guy is on the way down, but maybe he reached the level he wanted and he is not having a love for boxing. He seems to like the whole commentator thing and talking. The amount of fighting he has done and the timing of it looks like he might just lack the motivation. Pacman is going to be the best 40 year old fighter we have seen since Hopkins.
I'm pretty sure Vegas oddsmakers already considered Thurman's unsteady showing against Lopez, his long layoff before that, his preoccupation with commentating and compared it with Manny's age, decline et cetera...and they thought Manny should be the underdog against Keith. So if Pacman wins, it should be significant. As for ranking it among other wins by a 40+yo boxer......some wins to consider: Foreman's KO of Moorer, Hopkins' wins post 40.
solely as a ww win, its just beating a bottom top 5 ww. as part of pacs whole legacy, its significant. its a measure of longevity, and longevity is a measure of greatness.
If Pac wins (which I think he will), unfortunately I suspect more comments will made about Thurman's failings instead of Manny's achievement. That said, Pac chose wisely when picking Thurman over Spence.