BOSTON -- Barring a setback, the Red Sox expect to send reliever Carson Smith on a rehab assignment to Double-A Portland on Saturday, manager John Farrell said Wednesday afternoon.

Smith threw 21 pitches to live batters Wednesday at Fenway Park. Farrell said the team will evaluate Smith on Thursday. If he checks out fine -- and with Smith, that hasn't always been a guarantee this season -- he'll pitch for Portland on Saturday.

"We anticipate him checking out fine," Farrell said.

Farrell said Smith will then join Triple-A Pawtucket on Monday for the start of a seven-game homestand at McCoy Stadium.

Smith underwent Tommy John surgery last May. His return to the mound has been halted twice -- first during Spring Training due to elbow tightness, then in mid-June due to shoulder discomfort.

The Red Sox hope Smith will eventually join newly-acquired Addison Reed, Matt Barnes and Joe Kelly as possible bullpen bridge options to get to Craig Kimbrel in the ninth inning.

Don't expect Smith to be pitching in Boston any time soon, though. Farrell said there's no timeline in place for Smith's return. Boston can keep Smith on a rehab assignment up to 30 days.

Having not pitched in over 18 months, Smith will need time to build endurance.

"While there's a lot of encouraging signs, the fact is he's going out and he'll need some appearances to continue to build endurance," Farrell said. "He'll probably go through some arm strength ebbs and flows. That's fully anticipated. This is an encouraging development."

Smith posted a 2.31 ERA in 70 appearances for the Mariners in 2015 -- his last full season in the majors.

David Price, Joe Kelly on the mend

Farrell said David Price (elbow inflammation) threw again on Wednesday, playing catch up to 90 feet. He made 25 throws from 60 feet on Tuesday. Joe Kelly was added to Pawtucket's roster on Wednesday and is expected to throw an inning of relief tonight, entering midway through the game for one clean inning.

Kelly faced hitters on Monday.