The 6-1, 245-pound Bush scored on a pair of 1-yard touchdowns in the Bears' 28-10 win over the Minnesota Vikings.
"He's a good player, and he has good size," coach Lovie Smith said. "He's got a little weight behind him, and that's what we brought Michael here for. A guy that size with pads down, there's a chance we're going to have success with him."
Bush finished with 21 carries for 60 yards as he subbed in for Matt Forte, who injured his ankle.
"I didn't see Matt (after the game) but hopefully he'll be back next week and we'll just all do what we did today," Bush said.
Bush rushed for 977 yards on 256 carries last season with the Oakland Raiders, mostly after a season-ending injury to Darren McFadden. Bush signed with the Bears in the offseason, and while he knew he would be Forte's backup, it's probably been hard to see his chances decrease. He's carried the ball 85 times for 306 yards this season.
"I've been down this road a million times," Bush said. "It's nothing new. I'll approach it the same way this week in practice.
"It's football. It's something I love and I'm just going to keep going at it. But it's tough seeing anybody go down. You want everybody to be healthy. It's a long season and we have five more games left, so the healthier we are the better this team is going to be."
Despite the circumstances of Forte's injury, Bush was pleased to be more involved.
"It felt really good being out there, getting in the flow and getting a good feel for (the game)," Bush said. "We started off early with the rotation so it was nice. This was big. We needed it, didn't want to lose three games in a row. Anytime you get a win is great so hopefully we get another streak going here. "