FORT MYERS, Fla. -- It has been inevitable for the past few weeks, but the Boston Red Sox on Thursday made it official: Eduardo Rodriguez will open the season on the disabled list.

Rodriguez emerged from his bullpen session Wednesday "relatively fine," according to manager John Farrell. But since it was the first time the young left-hander had been on a mound since dislocating his right kneecap Feb. 27, the Red Sox will continue to take things slowly as Rodriguez normalizes his delivery and builds his arm strength.

"He is not going to be ready for the start of the season," Farrell said. "We want to make sure his stride direction, his stride length, all of those are normal. We then build the intensity on top of that."

Eduardo Rodriguez "needs spring training," manager John Farrell said, and will start the season on the DL before he can return to the rotation for the Red Sox. Greg M. Cooper/USA TODAY Sports

With Rodriguez sidelined for the season's first few weeks, left-handers Henry Owens and Roenis Elias and knuckleballer Steven Wright are the leading candidates to be his stand-in.

"It's like when you was a little kid and you're going to the playground and you see everybody playing and your mom tells you, 'No, you're not going to play.' That's how I feel right now," Rodriguez said. "Everybody's playing with their toys and I can't."

Standing at his locker nearby, closer Craig Kimbrel handed Rodriguez a baseball, a gesture that provoked laughter from both pitchers.

The Red Sox can joke about Rodriguez's plight because they don't believe he will miss more than a few weeks. He will remain in what Farrell described as "a bullpen phase," throwing off a mound again Friday, Monday and every other day thereafter until the team is confident his delivery is sound enough to ramp up his arm strength.

From there, Rodriguez will likely have to face hitters in a live batting practice activity before starting a few exhibition games and making a minor-league rehab assignment.

On Wednesday, Rodriguez threw a modified bullpen session in which the catcher was positioned closer than usual.

"That forces your stride to be a little bit shorter than normal," Farrell said. "We've got to get back to a normal stride."

Said Rodriguez: "That was a test (Wednesday) to see on what page we are, and it was pretty good. I was just testing myself to see how my leg is, and it was good."

With early-season days off on April 5 and April 14, the Red Sox can arrange their rotation to minimize the need for a fifth starter. But Farrell also wasn't ready to estimate how many starts Rodriguez will actually miss.

"There are steps that we have to go through here, and I don't have an exact number of days that he'll have to advance through each of those phases," Farrell said. "I can tell you this: Any time we get a starting pitcher that goes out on rehab, you're getting them to 80-90 pitches. You can't bring them back with the potential that they overtax a bullpen. We've got to build to that point. He needs spring training."

Rodriguez went 10-6 with a 3.85 ERA in 21 starts last season and became the first Red Sox rookie lefty to win at least 10 games since John Curtis in 1972.