CINCINNATI -- In another development in his left knee injury status, the Reds reversed their Minor League optioning of Nick Senzel, placing him back on the injured list Thursday.

Senzel was on a rehab assignment with Triple-A Louisville through last week as he worked back from left knee surgery. He was activated from the 60-day IL on Sunday and optioned to Louisville.

“He deemed himself healthy the five days prior to trying to come back,” Reds general manager Nick Krall explained. “At the end of the [rehab] time, he was not healthy. He was trying to push through it. He didn’t want to say anything. We had him go see the doctor. He still had fluid in his knee.”

The rule allowed the Reds to not lose the option on Senzel, who had multiple medical opinions this week.

“It’s like this transaction never happened. You basically go back to Sunday and he is still on the IL,” Krall said.

There is no timetable on when Senzel might be able to return.

“Our goal is to get him healthy and not try to push through this,” Krall said.

The Reds initially placed Senzel on the IL May 21 and he had arthroscopic surgery to clean out damaged cartilage on the undersurface of the patella a few days later. The original hope was that he could return just after the All-Star break in mid-July. Tyler Naquin has become the regular center fielder for Cincinnati in Senzel's absence.

Senzel, 26, will head to the team’s complex in Goodyear, Ariz., for more rehab and physical therapy. That decision was made, Krall said, to keep him on a more consistent schedule with the staff rather than having to travel with the big league club and its physical therapists and training staff.

If his knee improves, Senzel would be allowed to begin a new 20-day rehab assignment after not playing for at least seven days. He went 10-for-35 (.286) in 10 games during his previous rehab assignment but did not play any games for Louisville after he was optioned.

The former No. 2 overall pick in the 2016 MLB Draft by the Reds, Senzel has had myriad injuries since reaching the big leagues in ’19. He’s missed significant time, including a torn labrum in his right shoulder that forced him to miss the final 23 games of his rookie year. He was also sidelined 27 games with COVID-19 last season.