HOUSTON — A couple of rough outings aren't LHP Jake McGee 's only problem.McGee was sent back to St. Petersburg on Wednesday to have his left knee checked, and the Rays are not sure how long he will be out of action.McGee felt something in the knee when delivering the 32nd pitch of his season-high 33-pitch outing Tuesday against the Astros, then told the training staff about it after the game."We're hopeful that it's not something that's too bad," manager Kevin Cash said.McGee wouldn't have been available Wednesday against the Astros and possibly not tonight against them, either. But just that the Rays sent him home for an MRI exam and a visit with team doctor Koco Eaton this morning would seem a sign of concern — and an indication that even in the best case, he is likely to miss several days — given that they head west after tonight's game for a weekend series with the A's.Asked if McGee was likely to join them in Oakland if no tears or other major issues were found, Cash said he wasn't sure. "Knowing we have (tonight's) game, then three and an off day, you never know what that could lead into," he said. BOXED IN: By allowing a 10th-inning homer to Marwin Gonzalez in Tuesday's 3-2 loss, RHP Brad Boxberger earned his major-league-reliever-high ninth loss overall and sixth walkoff loss, a team record and the most in the majors since Brad Lidge had six in 2009 for the Phillies. (The last with seven was Roger McDowell for the 1992 Dodgers.)"It's frustrating," Boxberger said.It's more so because Boxberger has been very effective when pitching for a save despite blowing one Wednesday. He has converted 29 of 33 chances with a 2-1 record and 1.18 ERA, but he has struggled in tie and other situations, going 2-8 with a 6.61 ERA. "It could be mental," Boxberger said. "I guess just the difference between keeping the lead versus keeping the tie could be part of it. But it's all a game we could win. To keep a tie or lead is kind of the same mentality out there. But there's just no room for a mistake in a tie game. With a lead, you do have a little bit of room if you make a mistake."Also frustrating is why Boxberger has had stretches of inconsistency. He said heavy use (48 mostly high-leverage innings over 53 games) may or may not be a factor, but he feels his mechanics are off. "I just haven't been able to locate like I was early in the year with my fastball and especially my changeup," he said. "I haven't been able to throw it where I want when I want, which I was able to do kind of all throughout last year and early this year. It's just a matter of figuring out what I need to do to get back on track."Cash said Boxberger's velocity and movement are still good, but hitters may be on to him a bit. "Maybe there's been some adjustment throughout the league that they've recognized and been able to lay off some specific pitches that he throws," Cash said. "Maybe he was getting more swings on them last year." ARCHED UP: All-Star RHP Chris Archer needed a full day to get over his frustrating Saturday start in Arlington, Texas, when he allowed eight runs (seven earned) on 11 hits over 51/3 innings against the Rangers. Then he started looking ahead to tonight's game and is confident he will do better.The Rangers took an aggressive approach, swinging early in the count at fastballs. Archer said he has started to see that from more teams but he doesn't need to change his style, just execute better. Archer needs six strikeouts to join LHPs Scott Kazmir and David Price and RHP James Shields as the only Rays with 200 in a season. BAD MATH: Wednesday's walkoff loss was the Rays' 10th, the most in the majors and one off the 2002 team record. It also dropped the Rays' record in extra innings to a majors-worst 2-10. MISCELLANY: SS Asdrubal Cabrera got a DH day Wednesday, with Tim Beckham starting at short. … The A's set their rotation for the weekend series: RHPs Chris Bassitt on Friday, ace Sonny Gray on Saturday and Kendall Graveman on Sunday. … LHP Jordan Norberto , who had been in the Rays organization since January 2014 working his way back from Tommy John surgery, was released from the Triple-A Durham roster, having gone 1-3 with a 4.96 ERA in 33 games, allowing 45 hits and 30 walks in 451/3 innings. … Breakout LHP Blake Snell allowed one hit (a homer) in five innings for Durham and has given up one earned run or none in all six of his Triple-A starts. 3B Richie Shaffer , just sent down by the Rays, homered twice in the Bulls' 17-2 win over Toledo (Tigers) on Wednesday.