BALTIMORE — Fresh off a pair of disappointing losses to the Yankees and Red Sox, the Orioles took another, more costly, blow on Thursday afternoon, this one knocking out the entire right side of their infield.

First baseman Derrek Lee (left oblique strain) and second baseman Brian Roberts were put on the disabled list, although given Roberts’ injury — concussion-like symptoms — the Orioles were able to place him on the newly enacted seven-day DL rather than the 15-day DL.

Neither player made himself available to the media following the announcement, although Lee said earlier in the afternoon that he understood that his presence on the active roster — while the team evaluated him on a daily basis — was handcuffing the Orioles’ bench.

“I understand the situation they are in,” Lee said of an O’s bullpen that exhausted every reliever — including Thursday’s originally scheduled starter, Jeremy Guthrie — in Wednesday’s 4-1 loss to the Yankees in 15 innings. “And at the end of the day, you have to do what’s best for your team.”

The veteran first baseman had been bothered by discomfort in his left side for weeks, but he aggravated the muscle further while running the bases during his first at-bat at Fenway Park on Monday. Roberts also started feeling the ill effects of his diagnosis in that game — which the Orioles lost despite holding a 6-0 lead in the sixth inning — following a headfirst slide into first base after he hit a ball off starter Daisuke Matsuzaka’s midsection in the top of the first.

Roberts, Baltimore’s leadoff hitter, was batting .221 with three homers and 19 RBIs in 39 games. he got off to a hot start this season but has struggled in May, which he opened with a 4-for-45 stretch through 11 games. Roberts had hit safely in his past three contests, going 5-for-15, before his headaches were brought to manager Buck Showalter’s attention.

While Lee’s trip to the DL was almost expected, given the nature of his injury, the news for Roberts is more surprising and potentially more devastating, given that the second baseman’s 2010 season ended due to a concussion from which he took months to fully recover.

“Any time you’re dealing with a concussion and heads and stuff, you’re concerned about it,” Showalter said of Roberts, who was limited to just 59 games last year due to a herniated disc in his lower back. “I was talking to Brian. this isn’t anything like the symptoms he was feeling last year. That’s good, but you still have those symptoms that we’re going to make sure that we have our arms around before we go forward.

“We’re hoping that it clears up and the doctors feel fine about it, and he’s a player [activated for] Tuesday.”

The timetable for Lee isn’t as optimistic; the first day he would be eligible to complete his stint on the DL — which is retroactive to Tuesday — is June 1. Lee, who was hitting .231 with 14 RBIs and 41 strikeouts, had tried to state his case to avoid the DL, citing his improvement on Wednesday.

But Lee hasn’t made any significant strides in recovery since then, and the Orioles — who went through a similar situation before losing shortstop J.J. Hardy to the DL for a month — weren’t willing to risk further injury.

“Talking to medical people, I don’t want to lose Derrek,” Showalter said. “I’d like to have him. he impacts our team in a lot of ways, but taking a chance on this?

“In my experience with these [injuries] over the years, there is usually a lot more going on there than you think. I hope not. I think there’s some talk about taking some form of X-rays or something that show certain inflammations to try and judge how bad it is.”

Given the dire straits of their bullpen following Wednesday’s loss, the O’s recalled left-hander Troy Patton and righty Chris Jakubauskas from Triple-A Norfolk to take the roster spots vacated by Lee and Roberts. Both pitchers were demoted after the game, and the O’s are expected to recall outfielder Nolan Reimold and purchase second baseman Ryan Adams’ contract from Triple-A Norfolk prior to Friday’s series opener against the Nationals.

The first moves of the day left the Orioles with a two-man bench for Thursday’s game: Luke Scott and catcher Matt Wieters, who was scheduled to get a rare day off.