MIAMI -- A big part of the Marlins’ rotation returned on Monday.

Pablo López, who has been out since June 15 with a right shoulder strain, was reinstated from the 10-day injury list and started the series opener against the Reds at Marlins Park.

“We’re going to fit him in tomorrow, and that way it gives everybody an extra day,” manager Don Mattingly announced Sunday. “He’s ready to go. We were happy with his last outing.”

Initially, Caleb Smith was slated to go Monday and Sandy Alcantara on Tuesday. Now, both of those two will slide to Tuesday and Wednesday, respectively. After that, it is unclear who will pitch on Thursday in the series finale with Cincinnati.

“It feels like forever since I’ve been on this mound,” Lopez said. “I’m really excited. I’ve been working on some things.”

In 14 starts, Lopez is 5-5 with a 4.23 ERA. In his last big league start, the 23-year-old threw seven innings, giving up three runs, in a 4-3 win over the Pirates on June 15.

Even though he missed more than two months, the Marlins never transferred Lopez to the 60-day IL. Because he remained on the 10-day IL, Lopez’s status does not impact the 40-man roster, which currently is at 39.

On Sunday, the Marlins did make a roster move, optioning reliever Tyler Kinley to Triple-A New Orleans, and reinstating right-hander Kyle Keller from the Baby Cakes.

“This move is all about having to have pitching today,” Mattingly said.

The Marlins' bullpen is thin after the starters worked just three innings on Friday and 3 2/3 innings on Saturday against the Phillies. Keller was expected to be a September callup anyway.

Getting Lopez back is significant in terms of Miami’s long-term, big picture. The right-hander was the club’s No. 3 starter to open the season. Of concern is the fact he’s dealt with shoulder issues the past two years.

“I’ve been thoroughly explaining my routine to the coaches, and the [medical] staff,” Lopez said.

As part of the adjustments to the routine he is doing, Lopez is running more.

In recent weeks, Lopez has been on a rehab assignment. Statistically, it hasn’t looked pretty. In 14 1/3 innings, he had an 8.79 ERA. But the final hurdle he cleared, in the eyes of the organization, came in his last rehab start. At New Orleans, he gave up one run in six innings, which convinced the front office that it was time.

“It’s always better to finish on a better note than I started,” Lopez said. “In the beginning, I was trying to find my way on the mound instead of just going out there competing and trying to get batters out.”

The Marlins are monitoring the innings of all their starters and are considering a six-man roster, but that wouldn’t happen until September when more reinforcements can be added.

There are just two scheduled off-days for the Marlins in the final month -- Sept. 2 and Sept. 19.

“With two off-days the rest of the year, we’re trying to figure ways to keep these guys' innings down,” Mattingly said.