I don't like Vinci as a -200 favorite in this spot. Knapp is no scrub on hardcourts. She's got an 8-2 record her last ten and losing only to top ten quality players in Wozniacki and Kerber. Knapp looked very impressive in beating Vesnina yesterday who in my opinion is actually better than Vinci on hard. Vinci is a master on clay but she can be vulnerable on this surface. She tends to use that slice backhand way too much and against a player that can return with pace like Knapp, it can backfire.
Very good value on taking Knapp today at +175.......best of luck.