SAN FRANCISCO -- The Big Unit is back, albeit as a reliever.
"We'll have to give him time, we know it," manager Bruce Bochy said. "Right now it'll be short, two or three innings. Hopefully we can gradually build this up."
The 46-year-old Johnson threw 53 pitches, including warmups, in a simulated game on Monday. He joined the Giants this year for his 22nd major league season to try to help the team reach the playoffs after a five-year absence. San Francisco pulled within 2½ games of the Rockies in the NL wild-card race with Tuesday's win.
"We missed him the last couple months," Barry Zito said after pitching the Giants to victory. "That's a golden bullet for us. We're excited. ... Energetically, he's great to have around."
The five-time Cy Young Award winner injured his left shoulder more than two months ago. Johnson last pitched July 5, when he came out of a game against Houston because of a left shoulder strain, an injury that was later called a torn rotator cuff.
Johnson, who has 4,869 strikeouts, is 8-6 with an ERA of 4.81 in 17 starts for San Francisco. In June, he became the 24th player in major league history to reach 300 wins.
"You're happy he's going to be back on the mound," lefty starter Jonathan Sanchez said. "He said he can't be in the rotation but he's another person to help and I know he can get two or three quality innings. We need him."
The Giants cleared roster room by placing right-handed reliever Justin Miller on the 60-day DL with inflammation in his throwing elbow, ending his season.
Miller, emotional and discouraged, said his elbow injury was a problem for him last year while with Florida. It's bothered him more in the last three weeks.
"It's something I tried to pitch through," said Miller, who went 3-3 with a 3.18 ERA in 44 outings this season. "It's tough. It's disappointing. I'll root these guys on. For me, it was the last thing I wanted to hear."