Although Spence is the favorite here, I'm thinking, with all other factors considered, that Tim could be worth the risk. Errol is old, hasn't been in the ring for 3 years, but rarely had fights in the past 5 years actually. And I remembered how he looked so easy against Crawford in his last fight despite the hype that the match was between 2 of the best fighters.
Tim isn't coming from a devastating defeat. I think he's recovered well after defeating Velazquez and Nurja. Spence, on the other hand, is. And it was a humiliating TKO. This must add to his ring rust. I hope he's in perfect shape, though.
Ring rust can be fixed by training, but the question is whether Spence has seen his shortcomings from his previous fight. We see that Spence got hit whenever he became aggressive against Crawford, which is a lack of defense during an aggressive move. If Spence had fixed that, he might have had a higher possibility of winning this match, but Tszyu, being naturally bigger, might put Spence in a very difficult situation.