Wins, postseason included (since 1975)
28 Bob Welch (A's, 1990)
28 John Smoltz (Braves, 1996)
27 Frank Viola (Twins, 1988)
27 Ron Guidry (Yankees, 1978)
27 Steve Carlton (Phillies, 1980)
26 Orel Hersheiser (Dodgers, 1988)
26 Curt Schilling (D-Backs, 2001)
26 Randy Johnson (D-Backs, 2001)
Justin Verlander has 20 wins going into September and is probably going to be pitching in the postseason (although the Tigers certainly know how to blow a big September lead). If the Tigers run away with the division, he might get rested a little more, but he'll still get at least 5 starts. He could easily join this list and move to the top if he continues his run (8 wins in his last 8 starts; 18-2 since May 1).
It's hard to imagine the Tigers doing well in the postseason without Verlander pitching well, so 30 wins, while unlikely, isn't out of the realm of possibility. He might have to carry the Tigers, 1988 Hersheiser-style, to the World Series, but he might be up to it this year.
Does anyone else have shot at 26 wins this year? Probably not. The only other possibility would be CC Sabathia, who is #2 in wins with 17 and is likely heading to the postseason. He would need an extraordinary run in September in October to get 9 more wins, but it is possible with 3 rounds of postseason.