MIAMI — The Phillies hoped to be without Aaron Altherr for only 10 days, but an MRI this week revealed a more severe injury to the outfielder's right hamstring. He will not return until sometime in August.

Altherr suffered a "mild-to-moderate" strain of his hamstring, Phillies assistant general manager Scott Proefrock said. The team's most productive hitter was hurt July 14 in Milwaukee. He will miss three or four weeks, Proefrock said.

It has been a breakout season for the 26-year-old Altherr. He is hitting .288 with an .898 OPS in 301 plate appearances. His absence will guarantee regular playing time for Nick Williams, although the rookie had already earned that status with his impressive play.

The outfield situation is somewhat muddled, for now. Howie Kendrick, sidelined since June 27 with his own hamstring injury, will head to double-A Reading on Thursday to begin what should be a brief minor-league rehab assignment. Kendrick could be activated sometime this weekend. That is relevant because the Phillies would like to trade Kendrick. It would help to have him on the field for a few games before the July 31 trade deadline.

Kendrick, 34, has played in just 33 of the team's 93 games to date.

Daniel Nava, another veteran outfielder who has produced, could also be dealt. He is the kind of player a contender would target closer to the deadline, a bat who would fill the role of a fifth outfielder on a team with postseason aspirations.

Nava collected four hits in Wednesday's 10-3 rout, his first four-hit game since 2013.

The Phillies will not promote prospect Dylan Cozens because of the current dynamic. They need at-bats for Kendrick and Nava to entice teams to trade for those players. Cozens has hit .238 with 22 homers and 125 strikeouts for triple-A Lehigh Valley.

So, for now, Nava and rookie Cameron Perkins will split time in left field until Kendrick returns. That could be as soon as Sunday. And, if there are trades, the Phillies could revisit the Cozens situation in August or September.

Extra bases

Nick Pivetta lasted 5 1/3 innings in an uneven outing. He surrendered two runs on solo homers to Giancarlo Stanton and Christian Yelich. He allowed another run to score on a two-out walk, single, and two wild pitches. "I feel like I didn't really have my best stuff today," Pivetta said. "I just battled through the day." His ERA is 5.58. … The Phillies had 20 hits in a game without a home run for the first time since May 2, 1990. … Luis Garcia extended his scoreless streak to 16 1/3 innings. He has a 2.31 ERA this season.