The two left-handers joined four Toronto righties on the DL. The Blue Jays, leading the AL with 11 victories, recalled right-hander Brian Bullington from Triple-A Las Vegas and will add another pitcher before Friday night's game at Chicago.
Bullington, drafted first overall by the Pittsburgh Pirates in 2002, was 1-1 with a 1.86 ERA in four relief appearances at Triple-A, striking out 10 and walking one in 9 2/3 innings.
Ryan was put on the DL with soreness between his shoulder and back, one day after he blew his second save chance of the season.
Ryan is 1-0 with an 11.12 ERA and two saves in six games. He gave up three runs in the ninth inning against Texas on Wednesday, blowing a 7-4 lead, but Toronto won 8-7 in 11 innings.
Manager Cito Gaston said Ryan's muscle soreness may be the reason for a drop in velocity this season. Ryan did not speak to reporters.
"I think he's been feeling it for a while," Gaston said. "He let us know after the game that he was having some problems there. He really can't get through the ball. It's kind of tight back there and it's keeping his arm from getting through."
Gaston said it was "more than likely" that left-hander Scott Downs will close while Ryan is sidelined. Ryan will go on a minor league rehab assignment before rejoining the Blue Jays.
Ryan is in the fourth year of a five-year, $47 million contract. He had ligament replacement surgery in his elbow after pitching in five games in 2007 and then returned to save 32 games for Toronto last year.
Romero was put on the DL with a strained muscle in his right side, retroactive to April 20.
Romero is 2-0 with a 1.71 ERA in three starts. He has struck out 13 and walked only four in 21 innings.
Toronto's first-round pick in the 2005 draft, he reached the major leagues for the first time this season, winning a spot in the starting rotation with a strong finish to spring training.
Romero said he first felt sore after sneezing before his start at Minnesota on April 14 but was able to pitch. He was still in pain after beating the Oakland Athletics on Sunday and underwent an MRI exam Wednesday that confirmed the injury.
"It's crazy," Romero said. "Even now I'm afraid to sneeze."
Romero beat Detroit in his debut on April 9 in a matchup with Tigers rookie right-hander Rick Porcello, a first-round pick in 2007. He hopes to resume throwing within two or three days.
Along with Ryan and Romero, Toronto already has four right-handers on the DL. Casey Janssen (shoulder) has been out since the spring, Jesse Litsch (forearm) went down after two starts and could miss six weeks, Dustin McGowan (shoulder) could miss the season after surgery and Shaun Marcum (elbow) isn't expected back until August after ligament replacement surgery.