Shohei Ohtani underwent successful surgery on his throwing right elbow on Monday, the Los Angeles Angels announced.

Angels general manager Billy Eppler said he had no timeline for Ohtani's rehab schedule as of yet but seemed optimistic about his expected return, most likely in the designated hitter's spot in 2019 and back in the pitching rotation in 2020.

"The doctor was pleased with what he saw and feels confident in the recovery process," Eppler was quoted as saying on

The 24-year-old Ohtani, who played in his rookie season in the major leagues, was placed on the disabled list with a Grade 2 sprain of the ulnar collateral ligament in June but made his comeback as a hitter the following month.

He returned to the mound and pitched on Sept. 2 but fresh damage was revealed in his elbow and Tommy John surgery was recommended.

Later on Monday, Ohtani was named the American League Rookie of the Month for September, joining Ichiro Suzuki (Seattle Mariners) in 2001 as the only Japanese to earn the first-year monthly honors multiple times.

Ohtani, who also earned Rookie of the Month honors in April, batted .310 with seven homers and 18 RBIs last month. He hit two homers on Sept. 5, the day doctors recommended that he get surgery.

A frontrunner for the AL Rookie of the Year Award, Ohtani went 4-2 with a 3.31 ERA in 10 starts this season.

As a batter, he hit .285 with 93 hits, 22 homers, 61 RBIs and 10 stolen bases in 104 games.