The Toronto Blue Jays' South Korean starter Ryu Hyun-jin has been sidelined with arm problems for the second time this season.

The Blue Jays placed Ryu on the 15-day injured list (IL) with left forearm inflammation Thursday (Toronto time), a day after the left-hander pitched four innings against the Chicago White Sox through pain.

Ryu gave up three runs -- one unearned -- on four hits in those four frames but was lifted after just 58 pitches with the Blue Jays leading 5-3. The team later announced Ryu was experiencing tightness in his left forearm.

Ryu had spent about a month on the IL, beginning in mid-April, with the same forearm issues and had felt elbow discomfort in his previous start last week against the Los Angeles Angels. Ryu admitted after the White Sox game that he regretted pitching in the game at all.

Ryu also recalled that the pain was similar to what he had felt after his second start of the season against the Oakland Athletics on April 16. He landed on the 10-day IL the following day and didn't return until May 14 against the Tampa Bay Rays.

Ryu made three starts in May, going 2-0 with a 1.72 ERA while showing an uptick in velocity, but concerns about his arm reemerged after the road start against the Angels on May 26.

He was taken out after five innings in that game, when he'd only thrown 65 pitches. Toronto manager Charlie Montoyo said after the game Ryu had tightness in his elbow.

Ryu still took his turn in the rotation against the White Sox, but there were red flags everywhere. Ryu only averaged 87.6 mph with his fastball, a full 2 mph slower than his season average. He once threw an 85.2 mph fastball, his slowest four-seamer all season. Ryu also did not throw his cutter after giving up a leadoff home run to A.J. Pollock on that pitch in the top of the first.

Montoyo praised Ryu postgame for battling through pain and giving the club four hard-earned innings, thus saving his taxed bullpen. It might have cost Ryu maybe a month of action, though, if his previous IL stint is any indication.

Ryu is 2-0 with a 5.33 ERA in six starts for the season.

The Blue Jays beat the White Sox 7-3 on Wednesday after Ryu's early exit and completed their three-game sweep with an 8-3 victory Thursday. At 30-20 for the year, they have now won a season-high eight straight games. (Yonhap)