Now, with two months of conservative treatment failing to get him anywhere near a major league game, Ryu is likely to undergo exploratory surgery on his troublesome shoulder, according to people familiar with his condition who spoke on the condition of anonymity.
The operation could end the 28-year-old South Korean's season before he has thrown a pitch.
Before the Dodgers' 2-0 defeat to the San Francisco Giants at AT&T Park on Tuesday, Andrew Friedman, the Dodgers' president of baseball operations, said Ryu hadn't decided what to do but acknowledged he was considering surgery.
"It hasn't progressed as quickly as we all hoped," Friedman said on a conference call.
Friedman said Ryu was consulting team doctors and that he expected the Dodgers to have more to say Wednesday about the pitcher's plans.
Losing Ryu for the season would almost certainly force the Dodgers to trade for a starting pitcher in the coming months, as their rotation is already without Brandon McCarthy, who recently underwent reconstructive elbow surgery.
"Any time you potentially lose two starters, you're always mindful of your depth," Friedman said. "Just like in the off-season, the focus is on adding starting pitching depth."
Friedman said he has braced himself for the possibility Ryu won't pitch this season.
"Mentally, I have been thinking for a little while, just because it's more helpful to err on that side," Friedman said.
For the first six-plus weeks of the season, the Dodgers have turned to their triple-A affiliate in Oklahoma City to replace Ryu and McCarthy.
The hard-throwing Frias made his fourth start of the season Tuesday and lowered his earned-run average to 2.55 by limiting the Giants to a run and seven hits over six innings.
Bolsinger has made three starts and has a 1.03 ERA.
"We're like anybody else," Manager Don Mattingly said. "You lose guys and you keep going. Carlos has stepped in at this point nicely. Mike Bolsinger has thrown the ball well for us."
But the Dodgers' starting pitchers have largely failed to pitch deep into games.
In the 37 games the Dodgers have played that weren't shortened by rain, the starter pitched six innings or less 26 times.
Although the Dodgers began Tuesday's game with the third-best bullpen ERA in the National League, the long-term success of their relievers could be compromised by their workload.
Ryu pitched 192 innings as a rookie in 2013 and 152 innings last year. He won 14 games in each of the two seasons and posted a combined ERA of 3.17.
However, the Dodgers knew he was an injury risk, as he was put on the disabled list twice last season because of shoulder-related problems. Nonetheless, the Dodgers signed two other pitchers with disconcerting medical histories over the off-season in McCarthy and Brett Anderson.
Ryu's troubles this year started in mid-March, when he was shut down after experience discomfort during a game of catch.
An MRI examination at the time revealed no structural damage to his shoulder.
Ryu suddenly found himself in something of a Catch-22. The only way he could find out what was wrong with his shoulder was to have surgery, but he didn't want to have surgery unless he knew what was wrong. Shoulder operations are considered riskier than elbow operations.
But Ryu has twice started a throwing program designed to rebuild his arm strength. Both times, he had to abandon the program because of continued discomfort.