Diaz's grand slam helped the Rangers jump out, 6-0, in the first inning and Eyre came to the rescue with two scoreless innings of relief at a time when the Tigers were threatening to wipe away that lead.
The Tigers had scored four runs off starter John Rheinecker to make it a two-run game and had two on with nobody out in the fourth when Rangers manager Ron Washington called on Eyre.
"I just didn't want the game to get tied right there," Washington said.
All Eyre had to do was face Gary Sheffield, Magglio Ordonez and Carlos Guillen.
"You're not thinking the game is on the line," Eyre said. "You're warming up and [bullpen coach Dom Chiti] tells you that you have the next hitter. You look up on the scoreboard and see it's Gary Sheffield and you think about making pitches."
He did just that. Sheffield fouled out to first baseman Mark Teixeira, Ordonez struck out and Guillen flied out to end the threat. Eyre did get into trouble in the fifth when a couple of singles by Ivan Rodriguez and Craig Monroe put runners at the corners with one out. But Eyre got Brandon Inge to hit into an inning-ending double play, and his ERA is now 2.70.
"He's meant a lot, especially when your starters can't get you into the fifth or sixth," Washington said. "He's been what we need. He's been a savior. He's done an excellent job for what we need."
Joquain Benoit, Akinori Otsuka and Eric Gagne followed Eyre with four more scoreless innings to finish off the victory. Rangers relievers now have a 3.49 ERA for the season. Benoit's 3.41 ERA is actually the highest in the bullpen among current relievers, a stark contrast to having every starter with an ERA over six.
Rheinecker couldn't reverse that. He faced 20 batters and 12 reached base on seven hits, four walks and a hit batter.
"The outing flat-out stunk," Rheinecker said. "I felt like I was a pitch behind all night ... definitely a bitter taste in my mouth. I didn't have fastball command."
He was still better than the Tigers starter. Anybody would have been. The Rangers jumped on Nate Robertson for six runs in the first and he was back in the dugout before he could get anybody out.
Jerry Hairston led off with a single and Michael Young and Mark Teixeira both worked walks. Sammy Sosa singled to left to give the Rangers lead and then Diaz crushed a 1-1 slider into the center-field seats for a grand slam.
A triple by Marlon Byrd ended Robertson's night and Ian Kinsler's sacrifice fly gave the Rangers a 6-0 lead. The six-run outburst was the most runs the Rangers have scored in the first inning this year and was the first time since May 22 that they had even scored in the first inning.
"I wanted more," Washington said. "That's a pretty good team over there and I wanted to put more runs up."
The grand slam was Diaz's second of the season and he's now hitting .294 with eight home runs and 20 RBIs in 22 games and 68 at-bats. He has struck out 22 times, including three times on Tuesday night and has yet to draw a walk. But his .691 slugging percentage is the highest on the team.
"I'm just taking advantage of my opportunities," Diaz said. "The more I play, the more I produce. I'm feeling more comfortable every day. I'm still chasing a few pitches out of the zone but I'm getting better."
The better he gets, the better chance he has of establishing a spot for himself in the outfield. Washington still has to find time for Frank Catalanotto, Kenny Lofton and Marlon Byrd, who has also had an impact since coming up from Triple-A. Brad Wilkerson is also expected to come off the disabled list at some point this weekend.
But Diaz isn't hurting his chances of being an intergral part of it.
"He's making a bid to get at-bats," Washington said. "We'll see how things work out as the season progresses. He's certainly done a great job."
Both he and Eyre have and the Rangers will take any and all bright spots they can find.