Sources: Sale expected to avoid Tommy John

Cora and Sale express frustration with umpires (0:39)

Alex Cora and Chris Sale were not pleased with home plate umpire Mike Estabrook's strike zone, with Sale outlining multiple pitches he thinks Estabrook missed. (0:39)

Boston Red Sox ace Chris Sale will miss the remainder of the regular season with a left elbow injury but is expected to avoid Tommy John surgery after a second opinion from Dr. James Andrews confirmed a previous diagnosis of inflammation, sources familiar with the situation told ESPN.

Sale flew to Florida to meet with Andrews on Monday, and he was treated with a platelet-rich plasma injection, Red Sox president Dave Dombrowski said in a statement. Following a recommended shutdown from throwing, Sale will be reevaluated by Andrews in six weeks.

Following his most recent start six days ago, Sale felt soreness in his elbow and underwent an MRI. Initial readings showed changes from the MRI Sale had in the spring but weren't clear enough to determine whether there is damage to his ulnar collateral ligament.

Monday's news delivered a collective sigh of relief in Boston, although it will be clearer in October how Sale responds to the treatment of rest and PRP biologics. The plasma, taken from a person's blood and spun in a centrifuge to isolate growth-factor-heavy platelets, is used to promote healing. In a number of cases, including that of New York Yankees starter Masahiro Tanaka, it has helped pitchers avoid elbow surgery.

Sale, who was placed on the 10-day injured list Saturday, is in the midst of the worst season of his 10-year career after signing a contract extension this spring that begins in 2020 and will pay him $145 million over five years. With a 6-11 record and 4.40 ERA, Sale has struggled despite an American League-best strikeout rate and an elite strikeout-to-walk ratio. He has had a problem with home runs, allowing 24 in 147⅓ innings, more than 60% higher than what he has averaged in his career.

Sale is coming off arguably the best season of his career, even though a shoulder injury sent him to the injured list twice in the second half of 2018. He nevertheless pitched to a 2.11 ERA, and although his stuff in the playoffs was substandard, Sale finished the Red Sox's dominant World Series run by striking out the side to clinch the championship.

The diminished velocity on Sale's fastball didn't scare the Red Sox away from handing him a long-term deal the year before he reached free agency. Boston, which is paying Sale $15 million this year as part of his first contract extension, owes him $30 million in 2020, 2021 and 2022 and $27.5 million in 2023 and 2024.

Early season velocity worries this year eventually waned, and occasional flashes of brilliance reminded of classic Sale. Just 10 days ago, Sale shut out the Los Angeles Angels for eight innings, allowing two hits, walking none and striking out 13. In his most recent start, against Cleveland, he punched out 12 in 6⅔ innings. His elbow began hurting the next day, sources said, and after informing the team of the issues on Friday, Sale underwent an MRI on Saturday.

Even with his struggles, the loss of Sale for any period of time will hurt the Red Sox as they try to claw back into the playoff picture. A 13-7 victory Sunday finished a sweep of Baltimore and extended their winning streak to five games, but the Red Sox still find themselves 6½ games behind the Rays for the second wild-card spot.