Phillies reliever Jesen Therrien might miss all of 2018

Jesen Therrien, a rookie Phillies reliever, rejoined his teammates Thursday with his right arm in a sling. That is because earlier this week he underwent Tommy John surgery, a procedure that could sideline him for the entire 2018 season.

"It's all good," Therrien said. "I'll come back stronger."

Therrien, 24, pushed his way into the bullpen picture with a strong minor-league season. But he will not be an option next season as the Phillies begin the process of separating which of their young relievers should remain on the roster through the winter.

The Phillies have 12 relievers — 13 if Mark Appel is counted — on their 40-man roster. They have tried some of them in high-leverage situations, like Thursday.

Ricardo Pinto pitched in the seventh inning of a one-run game and surrendered two runs to raise his ERA to 7.89. Hoby Milner (2.28 ERA) has earned more assignments, although his future could be as a lefty specialist because of his extreme splits. Victor Arano (1.69 ERA) lacked command Thursday when he walked two batters, but he struck out two others and escaped a scoreless inning.

They could look to insert Yacksel Rios (5.11 ERA) into some tighter spots in the season's nine remaining games. There were a few priorities for this final month, but a bullpen evaluation was one of the more pressing tasks.

"It's outstanding, especially for guys like Pinto and Rios and Arano and even Hoby Milner in his first year," Mackanin said. "To get this kind of experience is worth a lot. That's a big part of this year."

When Therrien reached the majors, his stuff was not the same. His fastball averaged 92.6 mph while with the Phillies, a tick or two below what he threw in the minors. He had an 8.35 ERA in 18 1/3 major-league innings. He was shut down from throwing after a Sept. 4 appearance against New York.

The typical recovery time for Tommy John surgery is between 12 and 18 months. Orthopedist James Andrews performed the surgery on Therrien.

The Phillies added Therrien to the roster at the end of July because he was slated to be a minor-league free agent after the season. They could remove him from the 40-man roster after the season, then re-sign him to a minor-league deal and pay for his rehab during 2018.

He will not be the only roster decision that shapes the bullpen.

The Phillies committed two errors in the 5-4 loss to the Dodgers. They led to two unearned runs. The team carried a 100-inning errorless streak into the game. It was the Phillies' longest since 2014. … Ben Lively, Henderson Alvarez, and Nick Pivetta will start this weekend in Atlanta during the final road trip of the season.