"It's encouraging," Maddon said before the Cubs took on the San Francisco Giants on Saturday. "When I went out there, I saw him crunched against the wall, laying on the ground. I was not too optimistic. When he stood up, that told us a lot."
In conjunction with the MRI results, the Cubs also activated outfielder Matt Szczur from the disabled list and designated right-hander Neil Ramirez for assignment.
"In order to compete in today's game, we needed one more position player," Maddon said. "It's an ongoing conversation and we felt we could always do it."
The moves give the Cubs five bench players, including Heyward, and 12 pitchers.
Szczur's second rehab start with Double-A Tennessee was rained out Friday night. He appeared in one game with the Smokies. Szczur, expected to join the team before Saturday's game time, is hitting .367 in 21 games with the Cubs this season.
Ramirez did not record a decision in eight games with the Cubs, with a 4.70 ERA.
"We felt we needed to do this now. We needed utility," Maddon said. "Neil is a wonderful young man and hopefully he will get an opportunity to play somewhere else."
Maddon said he was not surprised by the good news about Heyward.
"You jut have to wait," he said. "All I know is it was a great play, from the extreme angle, the distance he covered and how he extended his body. That set up the game for us."
Rick Eymer is a contributor to MLB.com and covered the Cubs on Saturday. This story was not subject to the approval of Major League Baseball or its clubs.