Leyland didn't accuse Robertson of hiding an injury, but he did say the pitcher's claims of sound health don't seem to jibe with what is happening on the field. Since his 3-2 victory over Baltimore on May 2, Robertson has gone 1-5 in six starts and allowed 26 runs in 25 2/3 innings (9.12 ERA).
"The ball is just not coming out of his hand the same way," Leyland said. "I'm going to look into it more. To this point, he's said that he's fine. I'm not going to question him, but it's obvious something's not right."
Robertson was 3-1 with a 2.48 ERA in his first six starts, with 12 walks and 23 strikeouts.
In his last six starts, the 29-year-old has walked 12, but only struck out 11.
"I'm just not getting a swing and a miss," Robertson said. "It's frustrating, because physically, I feel fine. But this is easily the worst stretch I've ever had in the big leagues, and what happened tonight has never happened to me. It's difficult."
So, too, is Leyland's decision about how to proceed.
A scheduled day off on Monday could enable the Tigers to skip Robertson's next turn, but would require a spot start on Sunday against the Mets from someone not currently in the rotation, or for Justin Verlander to pitch that game on three days' rest. Verlander is scheduled to pitch on Wednesday night at Texas.
Earlier Tuesday, Rogers threw his first simulated game since his March 30 surgery to relieve a blood clot and arterial impingements. Though it went well, the veteran lefty still is likely to need at least a couple of Minor League rehab starts to build up his pitch count and endurance. The Tigers hope to have Rogers back by the end of June, but are leery of rushing the 42-year-old back faster than that.
The options aren't appealing, but neither is the alternative of letting Robertson continue to cost the Tigers winnable games and tax their bullpen.
"At some point, I've got to make an adjustment [to the rotation]," Leyland said. "We can't continue to have this go on, because no bullpen can survive that. It's that simple."
Leyland said Robertson's velocity appears to have dropped slightly since last year, when he was 13-13 with a 3.84 ERA.
"From what we've seen, it's down some," the manager admitted. "I've got to look into whether everything is right [physically], because that's hard for me to believe.
"I'm very concerned. Robertson gives us everything he's got. But right now, what he's got isn't very good."
On Tuesday, Robertson delighted a crowd of 32,003 at Rangers Ballpark in Arlington by digging an insurmountable early hole for his team. He faced six batters and allowed all six to score without recording an out, giving way to reliever Jason Grilli.
A single by Jerry Hairston Jr. and walks to Michael Young and Mark Teixeira loaded the bases, and Sammy Sosa's RBI single drew first blood for the Rangers. A grand slam by Victor Diaz put Texas up 5-0, and Robertson was relieved after Marlon Byrd followed with a triple.
The sixth run was charged to Robertson (4-6) when Grilli gave up a sacrifice fly. Just like that, Robertson's ERA swelled from 4.25 to 5.07.
"I gotta give my team a chance to win," Robertson said. "I didn't do that tonight."
Rangers left-hander John Rheinecker, called up to make an emergency start in place of sore-armed Vicente Padilla, nearly gave the lead away. He allowed three runs in the top of the second inning and a fourth run on a leadoff homer by Brandon Inge in the fourth.
Ivan Rodriguez had a chance to score from second on a fifth-inning liner by Craig Monroe, but the ball caromed off the base of the right-field wall for a long single and Rodriguez only made it to third. He was stranded there when Inge grounded into an inning-ending double play.
"We had some opportunities," Leyland said, "but their bullpen shut us down."
Four Texas relievers held Detroit scoreless on two hits for the final six innings. The last-place Rangers won for only the third time in their last 13 games.
Rangers second baseman Ian Kinsler singled, stole two bases and scored an insurance run in the eighth off right-hander Fernando Rodney, who was making his first appearance since May 20.
The loss, coupled with Cleveland's 1-0 victory over Kansas City, dropped the second-place Tigers 3 1/2 games behind the AL Central-leading Indians.
The last Tigers starter who could not record an out also was Robertson. On July 8, 2005, he threw his first pitch at Tampa Bay behind Rays leadoff man Carl Crawford and was ejected.
Only eight times in the history of the Rangers has an opposing starter unable to record an out. This was the first such instance since May 1989, and the six runs allowed by Robertson made his the worst such performance on that ignominious list.