Pelfrey will now pitch Friday against the Astros; Niese will start in his place Thursday against the Marlins. Pat Misch, who was to miss a turn in the rotation, will give both of them an extra day by taking his regular turn Wednesday against the Marlins.
"Our starters have given us some length lately," Manuel said. "When they start giving you length late in the season, if you have a chance to give them a day, you've got to give them a day."
Equally pressing is the status of Niese, who threw 120 innings between two levels last season but has already eclipsed that mark and is on pace to throw roughly 180 innings this season. Though the Mets have addressed the possibility of limiting Niese's innings down the stretch, Manuel dismissed that notion on Tuesday.
"We touch on that kind of stuff all the time, but we haven't really sat down and put anything in ink," Manuel said. "I think a lot depends on if we see a diminished product, if we see fatigue. Then I think we'll probably visit it with some sincerity."
Most young pitchers who eclipse their innings totals by wide margins, however, do not show diminished returns until the following season. Pelfrey, for example, was sensational down the stretch as a 24-year-old in 2008, while eclipsing his previous career high by nearly 50 innings. The next year, his ERA ballooned from 3.72 to 5.03.
Considering the recent examples of players such as Pelfrey and Justin Verlander of the Tigers, many teams have taken a hard line on innings totals with their young pitchers. The Yankees, for example, have gone out of their way to limit the innings of Phil Hughes -- currently one of the best starters in the American League -- in the height of a pennant race.
The Mets don't have nearly as much to play for at this point in the season. But they also face a different sort of decision with Niese, whose height, weight and history all play a role. Niese threw a career-high 180 innings two years ago, and might have eclipsed that total last year had he not missed much of the season with a right hamstring tear.