But Schmeichel, who played in the reserves' 1-0 defeat by Liverpool on Tuesday, has still travelled with the senior squad in order to gain some valuable experience.
Claudio Reyna is back after suffering with flu while Danny Tiatto and Eyal Berkovic are the only two senior players out through injury.
Seaman's availability will provide a boost for Keegan in what is a massive game for the club.
The City boss told the official club site: "You can’t underestimate the importance of this game for the club and the timing too is important because if we get through this round then we can put it away for a couple of months.
"We could hopefully get drawn against someone exciting and we could then put it on the back burner and concentrate on the League, Carling Cup and FA Cup.
"It is very important for the club but we will have to be good enough to get through."
After taking an early lead in the home leg the Poles claimed an away goal and City were lucky to hang on for a 1-1 draw.
"We have a lot of work to do," Keegan added. "They are a small club but a dangerous club.
"It is a small ground and it is the same for us both. It is a big playing surface and the weather at the moment we are told is quite good there."