Concern about the number of innings Mike Pelfrey has pitched this season have prompted the Mets to push back the start after his outing this Monday. As a result, the young right-hander will throw Monday against the Astros, then not again until Sept. 3 in Milwaukee. That will give Pelfrey eight days between starts. The Mets think he needs it having already thrown a career-high 154 innings this season. Brian Stokes, who already has one spot start this season, is likely to replace Pelfrey in what would have been Pelfrey’s regular turn Aug. 31 in Florida.