Gonzalez singled off Jeff Francis to lead off the four-run fifth. Juan Uribe followed with a fly to shallow right. Right fielder Jay Bruce called off second baseman Brandon Phillips but slipped and the ball fell for a single. After Joc Pederson walked, Guerrero homered to left.
“He looked stiff at first. It’s from not playing in a while,” Mattingly said. “I’ve watched his at bats lately and he looks more fluid and seems more comfortable.”
Gonzalez homered off Sam LeCure started another four-run inning in the sixth.
The Reds commited two errors in addition to the missed fly ball that was ruled a hit.
“We’ve made a couple of mistakes that have led to big innings,” Reds manager Bryan Price said. “We need to execute better.”
Ryu finished with three strikeouts, all in the third. He walked Todd Frazier but got a double-play ball to finish strong.