Silva (9-4, 3.86 ERA) has not pitched beyond the second inning in his past two starts, giving up 11 runs on 13 hits and five walks over 2 1/3 innings.
"He's been working with some things with Larry, and it might give him a little time to continue to work, but we'll see," manager Lou Piniella.
Ryan Dempster (8-7, 3.70 ERA) will start on Sunday in the series finale against the St. Louis Cardinals. He'll be pitching on normal rest because of the off-day Thursday.
Left-hander John Grabow, on the disabled list because of a sprained left knee, threw in the bullpen, but he is not close to returning. He has been sidelined since June 29.
Brian Schlitter, a right-hander who impressed Piniella in his brief callup in June, was to throw Wednesday for Triple-A Iowa. He's on the disabled list with a right shoulder impingement.