I don't even know how Raonic managed to lose to Montanes, but I don't see him upsetting two players B2B, considering how bad he's been playing. The price is pretty low on Tips, which is kinda fishy - but not gonna over-think this. Tips did get some clay experience in the Davis Cup so he shouldn't be too rusty.
Nishikori is 0-1 H2H against Mathieu but its irrelevant as that was in 2009, and the Japanese is playing much better this year. He should be able to beat a 350 ranked opponent.