PHILADELPHIA -- Expected to be nearing a return to the lineup for the first time in three months, Nick Senzel was indeed reinstated from the 60-day injured list by the Reds prior to Sunday's 7-4 win over the Phillies -- only to be optioned to Triple-A Louisville.

Senzel, who underwent left knee surgery in May, is fully healthy and had gone 9-for-25 (.360) with four extra-base hits over his last six rehab games with Louisville. Yet with Tyler Naquin's emergence in center field and the club already dealing with a logjam in the infield, there simply wasn't a viable spot on the big league roster for the club's 2021 Opening Day center fielder. It also helped that Senzel had Minor League options remaining.

"Well, right now, if we bring him to the club, who goes down?" general manager Nick Krall said. "There's only so many players that are optionable right now, and I think that's the main factor -- he had some flexibility. We felt the guys up here were playing well, so we want to keep this group together for right now and keep moving forward."

That may not be so easy, however, after Jesse Winker departed Sunday's game in the third inning after aggravating the intercostal strain that had kept him out of the lineup the previous two days. He'll undergo more testing on Monday to determine the next steps, but his potential absence could suddenly open a door that was seemingly closed.

At the time of Krall's comments before Sunday's game, the Reds looked set with Winker in left field, Nick Castellanos holding down right field and Naquin in center. Shogo Akiyama and Aristides Aquino -- who took over for Castellanos (ejected) and Winker, respectively, on Sunday -- are the other outfielders on the active roster.

Though Senzel had started taking reps at second and third prior to his injury -- and saw time at shortstop during his rehab -- the Reds have five potential starters for four infield spots as it is. With the return of Mike Moustakas last week, manager David Bell is already juggling playing time for Moustakas and Eugenio Suárez at third, with Joey Votto at first, Jonathan India at second and Kyle Farmer at short.

"Tyler Naquin's played really well in that position, and then our infield's played well, as well," Krall said. "So I wouldn't tell you he would be starting, otherwise he'd be here."

At that point, it became a question of whether it was better to bring Senzel up as another bench bat or keep 14 pitchers on the roster. With Sunday marking the Reds' 13th game in a stretch of playing 20 straight days, they opted to go with the latter option.

"Having an extra reliever right now, as we go through a 20-game stretch, is really important for us," Krall said. "Especially as guys get tired in August."

Making the situation even murkier is the fact that rosters this season will expand by only two players -- from 26 to 28 -- in September. That's different than past years, when teams had been allowed to carry up to 40 players in September (this changed in 2020 due to COVID restrictions, and the 28-player rule was put in place for '21).

"I think he can be a contributor on this club when rosters expand or, you know, if there's an injury or something like that -- I think that he's going to be an option to be brought up," Krall said. "I think we're going to have to make some tough decisions as we get to September. We have a handful of guys who are playing well, but you only get two extra roster spots this year, as opposed to two years ago when you could bring up all 40."

A key contender for one of those spots figures to be shortstop José Barrero, the club's No. 4 prospect. Barrero entered Sunday with a .313/.398/.600 slash line to go with 11 homers and seven stolen bases over 39 games since being promoted to Louisville in late June.

"The most important thing is to continue to get him at-bats. He's still getting comfortable there," Krall said. "He's doing really well there obviously. Whether he's ready to come here in September, we'll have those discussions over the next few weeks."