Bryce Harper said he still couldn't close his glove around a ball. (AP)

WASHINGTON -- Nationals left fielder Bryce Harper (torn left thumb ligament) confirmed Thursday that there is no set timetable for his return.

Harper suffered his injury sliding into third base against the Padres on April 25. He was placed on the 15-day disabled list two days later and has missed 33 games. Manager Matt Williams said Wednesday he hopes for a July 1 return for Harper, but the 21-year-old slugger is not as set on any specific date.

"If it takes me till after the All-Star break or a month after the All-Star break, then it's going to take me that long," Harper said. "I'm not going to rush back. I'm not going to do anything stupid. I'm just going to see how I feel and go from there."

Harper said he still couldn't close his glove around a baseball, which has prevented him from doing any work in the outfield, taking ground balls and playing catch. Harper also hasn't taken swings with two hands yet, and he said the vibration of the bat would perhaps be the biggest test for him in his return.

"I don't really have that itching feel," Harper said. "Of course, I want to play and it [stinks] having to sit inside the dugout and watch my team without me out there. But nothing's been too bad."

Harper took hand-rolled ground balls and threw Tuesday in an effort to maintain motion. He has also been working with the team therapist, doing strengthening and flexibility exercises for his injured ligament.

"I'm just going to take as much time as I can to be where I need to be," Harper said, "to be 100 percent or close to 100 percent when I come back so I can help this team."

Ryan Zimmerman overcame his fractured thumb and returned to the lineup Tuesday night against the Phillies, making his first career start in left field -- Harper's position. In terms of fitting in, Harper said he would like to play center field more than anywhere else on field. He also joked about getting some time behind the plate to give Wilson Ramos some rest.

"My numbers are a lot better in center field," Harper said. "I feel good there. But of course we have Denard Span, who's one of the best center fielders in the game, if not the best. So I'll play anywhere they want me."

Desmond out of lineup, Zimmerman stays in left

PHI@WSH: Desmond goes yard to lead off the 6th

WASHINGTON -- Nationals manager Matt Williams gave shortstop Ian Desmond the day off for the series finale against the Phillies on Thursday afternoon because of general soreness following Wednesday's night's 8-4 win, which featured a 1-hour, 48-minute rain delay.

Second baseman Danny Espinosa moved to shortstop to replace Desmond, while typical third baseman Anthony Rendon moved to second base. Ryan Zimmerman remained in left field for his third straight game and infielder Kevin Frandsen started at third base.

"Hopefully, it won't be too long that Anthony may have to play second base," Williams said. "That would mean that Harp's back."

Williams said Zimmerman is still an option at third base, but it's important to be mindful of his recently healed thumb and throwing shoulder.

"If he came back into third base, he's been doing it a long time, it's not like it's going to be foreign," Williams said. "At some point, he's going to be back in there."