Miller was activated Friday after being out because of inflammation in his right knee. The left-hander, who was on the 60-day disabled list, has been sidelined since May 26. Miller also missed time earlier in the season with a strained left hamstring.
The Indians hold a comfortable lead in the AL Central, but the team has much bigger plans than reaching the postseason and needs Miller to be a dominant force again to get there.
"Ideally, we have a lot more business to take care of," he said before Friday's game against the Los Angeles Angels. "You want to be sharp at the end of the year because this team has very high aspirations, and the goal is to win more than just the division in the regular season."
Miller, a key part of Cleveland's bullpen since being acquired in 2016, is 1-3 with one save and a 4.40 ERA in 14 appearances. He pitched 10 scoreless innings to begin the season, but was on the DL from April 26 to May 11 with the hamstring injury and struggled after returning.
"I don't want to miss any time, but I feel like the team has done pretty well, and it's important for me to get back and pitch the way I'm capable of," he said. "I've pitched when I'm not 100 percent, and it was getting pretty hard. So we wanted to make sure I came back strong, crisp and ready to go."
Cleveland's bullpen is 14th in the AL with a 4.98 ERA, but relievers Brad Hand and Adam Cimber were acquired from San Diego during the All-Star break. Miller's return will give manager Terry Francona another option along with Cody Allen.
"Just having Andrew back is exciting, and we know it might not be midseason form yet, but he'll get there," Francona said. "You start thinking about shortening games and some of those guys back at the end there can do that."
Right-hander Zach McAllister, who was 1-2 with a 4.97 ERA in 41 appearances, was designated for assignment. He has spent parts of the last eight years with the Indians and is a free agent after the season.
Outfielder Tyler Naquin underwent right hip surgery on Thursday and is expected to resume baseball activities in 6 to 10 weeks. He batted .264 with three home runs and 23 RBIs in 61 games.