If he isn't too rusty, Jhonny Peralta should be on the Tigers postseason roster.
That's my way of saying, don't let concerns over his suspension bother you too much, nor should you worry about the precedent set by the Giants last season.
First, Peralta's suspension was not for a positive drug test this season. It was for evidence linking him to the Biogenesis scandal last year. So far as we know, this season's performance was not due to any enhancements at all.
Second, if you're the type to think the season's corrupted by having Peralta on the roster, that ship has already sailed. The Tigers were a .626 team at the time of Peralta's suspension, a .569 team without him. Obviously you cannot and should not tie a team's outcome that strongly to one player. There are other factors, a host of players who are injured, for instance. But the stat is right there in front of your face. The Tigers were the best team in the division with Peralta, and they're trailing the Royals since his suspension.
Third, the Tigers really do need him back, should he show them he's not rusty. Right now, struggling players like Matt Tuiasosopo or Hernan Perez appear in line to make the postseason. It's not exactly a high hurdle to get over. Jose Iglesias is battling shin splints. What if he isn't healthy in the postseason? The Tigers cannot afford to slam the door shut if Peralta can help.
Peralta admitted wrongdoing. He accepted his punishment. With three games left in the regular season, the slate is wiped clean. The Tigers owe it to themselves and their fans the best shot in the postseason. They look good on paper, but there's no guarantees they'll get another chance this good in the future.