Fognini made several unforced errors at the start of the match to hand de Bakker a 5-1 lead, but then won nine consecutive games to take control. Fognini earned his 11th consecutive singles victory, after winning titles in Stuttgart and Hamburg.
"I was not consistent at the beginning, obviously I did not play great tennis. But after 10 matches in a row in two weeks, it could be expected," he said. "I started slow, then I started to fight for every point."
Klizan was up 4-1 in the third set, then failed to serve out the match at 6-5 before clinching the win in the tiebreaker.
Mayer took a 4-1 lead at the start, but Klizan won 10 of 12 games after dropping the first set.