How much is up to offensive coordinator Jimmy Raye.
"I told Jimmy, he and Isaac will talk and figure out exactly how it will be played out," Singletary said during his Friday news conference. "Isaac will be up, and I know he'll be an honorary captain. What happens after that, we'll see. Maybe he'll play, maybe he won't. We'll see."
Bruce missed the previous five games because of an ankle injury, and it appears his NFL career is coming to a close after 16 seasons, 14 of which he spent with the Rams. The 49ers' receivers, specifically Josh Morgan, came to Singletary earlier in the week and pleaded for Bruce to play in St. Louis, as a tribute to a man who ranks second in NFL history with 15,208 receiving yards.
Singletary was swayed by the gesture.
"All I know is that I want it to be very respectful," the coach said. "The wideouts stepping up and coming to me about it obviously shows how they feel about him. I think we all feel that way about Isaac, but at the same time, it's just a matter of going the extra mile. I wanted to honor that, and I think Isaac and I are on the same page. I think when the guys did that, it's one of those things that he wanted to honor it as well. From there, we'll let things play out."
Singletary added that Bruce definitely will be on the field for the coin toss Sunday, but he also "could play the first play or he could play the first series."
Singletary wasn't as forthcoming about kicker Ricky Schmitt, who joined the team last week after starter Joe Nedney sustained a hamstring injury. Schmitt made 2 of 3 field-goal attempts during a 20-6 victory over the Detroit Lions last Sunday, then came down with a groin injury that prevented him from practicing Thursday and Friday.
"I think it's one of those things where we really just have to wait and play it out," Singletary said. "I think the most important thing that we have to do is make sure we cover ourselves on the other end of that. We may have to look at another kicker, depending on how that unfolds between now and game time."
When continually pushed about whether or not Schmitt will make the trip to St. Louis, Singletary said: "I have no idea. I don't know. I don't care. I just want a guy that can kick. That's it. Simple as that. That's it."