ARLINGTON, Texas -- These days, winning is tough for the Texas Rangers even after building a big lead.
Rangers replacement starter John Rheinecker got some outs, but he wasn't much better than Robertson, allowing 12 base runners (seven hits, four walks and a hit batter) and four runs in three-plus innings.
"The outing stunk," said Rheinecker, activated from the disabled list after Vicente Padilla was scratched because of an irritated right triceps. "The fastball command was definitely not there."
Instead of an easy victory at home for Texas, Rheinecker gave up three runs on four straight hits to start the second. He was done after the first three Detroit batters reached in the fourth, including Brandon Inge's leadoff homer that cut the deficit to 6-4.
"They kept him in trouble," manager Ron Washington said. "It got a point we had to see what we could do to keep the game where it was."
Willie Eyre (2-2) got out of the two-on jam by retiring Gary Sheffield, Magglio Ordonez and Carlos Guillen in order, then pitched another shutout inning. Eric Gagne pitched the ninth for his fifth save in five chances.
The slam by Diaz came right after an RBI single by Sammy Sosa, who has gone two weeks without a homer to remain stuck at 598 for his career. Marlon Byrd followed with a triple into the right-center field gap and Robertson (4-6) was done after six batters, 30 pitches and no outs.
"He wasn't very good," Tigers manager Jim Leyland said. "I can't explain it. I'm going to talk to him and look into it some more. The ball isn't coming out of his hand right. At some point you've got to make an adjustment. I don't know what to do with Nate right now."
Robertson has lost four of his five starts.
"I felt pretty strong going in tonight," he said. "There's nothing hindering me physically."
It was the first time in 10 years that an opposing starter failed to retire a Rangers batter, since Minnesota's Roy P. Smith gave up four runs and five hits without an out May 26, 1987.
Robertson was also the last Tigers starter who didn't record an out, but that was a different circumstance. The left-hander had a 4-0 lead at Tampa Bay when he was ejected July 8, 2005, after his only pitch was behind Carl Crawford, apparently in retaliation for teammate Placido Polanco getting hit by the first pitch of the game.
Michael Young went 4-for-4 for Texas (21-37), which lost five straight home games before its just-completed 2-5 road trip.
The Rangers hadn't scored in the first inning since May 23 against Minnesota, a night after Sosa hit his last homer. Texas had been outscored 44-11 in the first inning this season and hadn't scored more than twice in an initial inning before their six-run outburst.
Leyland visited the mound after Robertson allowed a hit and two walks against the first three batters. Sosa then hit a ground-ball single through the left side of the infield and Diaz hit his second career grand slam, both this season.
Ian Kinsler, the first batter faced by reliever Jason Grilli, hit a sacrifice fly to drive home Byrd and make it 6-0. Grilli pitched four scoreless innings with five strikeouts before Zach Miner struck out two in his two innings.
Inge, who missed Detroit's last five games because of a small chip fracture in his left big toe, was 2-for-4. Before his ninth homer, he his run-scoring hit in the second was the third of four straight singles to start that inning before Sheffield's bases-loaded walk and Ordonez's sac fly.
- Rheinecker pitched 11 scoreless innings in two rehabilitation starts for Triple-A Oklahoma after starting the season on the DL with a strained back.
- Sosa is 6-for-40 (.150) with 12 strikeouts since his last home run, a solo shot in the second inning against Minnesota on May 22.
- Diaz, who homered twice Sunday, struck out three times after his grand slam.
- Tigers SS Carlos Guillen was back in the lineup after missing four games with a mild left groin strain. He went 0-for-4.
- Kinsler led off the eighth with a hit and then stole second and third base. He has 10 steals without being caught this season.