CINCINNATI -- Three days into September, the Phillies have added eight players to their roster, including two more on Tuesday when right-hander Nick Pivetta and infielder Jose Pirela were called up from triple-A Lehigh Valley.

And still, Spencer Howard waits in the minor leagues.

Rather than making his big-league debut in the midst of a wild-card race, the right-hander is expected to start Game 1 of double-A Reading’s Eastern League playoff series against Trenton on Wednesday night. The Phillies haven’t categorically ruled out calling up their 23-year-old top pitching prospect, although it remains highly unlikely.

Howard missed nearly two months in the middle of the season with shoulder soreness. But he was lights-out upon his return to high-A Clearwater, and after getting promoted to Reading last month, he posted a 2.35 earned-run average and a 38-to-9 strikeouts-to-walks ratio in 30 2/3 innings over a half-dozen starts.

But while there's a chance that Howard could give the Phillies a boost in their attempt to overtake the Chicago Cubs for the second wild-card spot in the National League, the club also continues to have reservations. Chief among them is whether Howard can adapt to the different baseball that is being used in the big leagues and triple-A. Several pitchers, including touted lefty Damon Jones, struggled to adapt after getting called up to triple-A this season.

Thus far, the Phillies have added three pitchers to the roster: Pivetta, right-hander Nick Vincent and lefty Cole Irvin. When third baseman Maikel Franco gets called up later this week, there will be 34 players on the roster. Asked if he expects to add any others, manager Gabe Kapler said, "No, but I wouldn't rule it out."

In other words, don't slam the door on Howard just yet. For now, though, the Phillies seem content to let him pitch postseason games for Reading before reporting in mid-September to the Arizona Fall League, a finishing school for top prospects.

Pivetta returns

Ten days ago, when Pivetta got optioned to triple-A for the second time this season, Kapler challenged him to be more accountable to himself and the Phillies. Upon his return, Kapler was preparing to sit down with Pivetta for a longer conversation about that subject.

"I wouldn't make too much of that, even though it's probably tempting to do so," Kapler said. "I think it's just something that we'll discuss and have a grown-up conversation about."

Pivetta has been the poster child for the struggles of the Phillies pitching staff. Pegged as a candidate to have a breakthrough season, he instead has posted a 5.38 ERA and twice lost his spot in the starting rotation.

Thanks to expanded rosters, Pivetta has a chance to salvage some of his season by getting big outs for the Phillies out of the bullpen. It's not yet clear what role he will play.

"My strong preference would be to ease him back in in kind of a mid- or low-leverage situation first and see how he looks," Kapler said. "But we might not have that luxury. We'll see."

Extra bases

Shortstop Jean Segura rejoined the Phillies Tuesday and was available off the bench after missing two games to attend his grandmother’s funeral in the Dominican Republic. ... Aaron Nola (12-4, 3.45 ERA) will start Wednesday night against Reds right-hander Trevor Bauer (10-12, 4.53).