WASHINGTON - The Phillies may need a rotation replacement for a significant amount of time, so they will call up the arm from a young triple-A staff that owns the most major-league experience.

Zach Eflin will start Tuesday at Citi Field against the Mets, Phillies manager Pete Mackanin said. The 23-year-old righthander replaces Clay Buchholz, who suffered an arm injury last week, in the Phillies rotation. It will mark Eflin's return to the majors following double knee surgeries last fall.

"Well," Mackanin said, "after what he did for us last year and he's healthy, he's the guy we wanted."

Eflin was scheduled to pitch Tuesday for triple-A Lehigh Valley, so the timing helped his cause. He has made two starts this season, one at high-A Clearwater and another at Lehigh Valley. That start lasted just 70 pitches, so Eflin may not be completely stretched out when he steps onto the mound Tuesday in New York.

Both the Phillies and Eflin were convinced in spring training that the knee surgeries to correct a chronic soreness could alter his career trajectory. Eflin, a former first-round pick, reached the majors while occasionally pitching through pain.

He posted a 5.54 ERA in 11 starts with the Phillies last season. He threw two complete games in a 17-day span last July. Through his first eight starts in the majors, Eflin owned a 3.40 ERA. His final three starts, in which he permitted 20 runs in 13 innings, forced the Phillies to place him on the disabled list and have a doctor examine his knees.

The Phillies had options other than Eflin. Jake Thompson made 10 starts for them last season. But his first two outings this season at triple A were gruesome; Thompson lasted just 21/3 innings in each one of his starts and has a 28.93 ERA. Nick Pivetta has started strong with a 0.69 ERA in 13 innings. He could be a consideration later, if needed.

Buchholz is expected to be sidelined for months, if not the entire season, with a partial tear of the flexor tendon in his right arm. He will receive a second opinion Monday from renowned orthopedist James Andrews. If Andrews recommends surgery, Buchholz will be lost for the season.

The Phillies did not put Buchholz on the disabled list sooner in order to add a player for the weekend series against Washington because Eflin was optioned to the minors less than 10 days ago and could return only if swapped for an injured player.

Extra bases

The backbreaking 6-4 loss to the Nationals on Sunday could have been worse; Odubel Herrera was not hurt in the ninth inning. He pinch-hit and moved a go-ahead run to third with a swinging bunt, but he appeared to suffer a leg injury while running to first. It was not serious, Mackanin said. Herrera needed to stretch. To be safe, Mackanin did not keep him in the game. . . . Freddy Galvis snapped an 0-for-16 stretch with his single in the fifth inning.