"If we come back tomorrow and win the ballgame, [the Athletics] will leave here the same way when they got here," Rangers manager Ron Washington said. "We feel like we're going to win tomorrow. We just didn't get it done tonight."
Perez was making his second start since replacing Scott Feldman in the rotation and couldn't get out of the first inning. He gave up five runs on six hits to eight batters before Washington summoned Roy Oswalt from the bullpen with two outs.
"I was trying to throw strikes, and they made adjustments," Perez said. "I was trying to get ahead with the breaking ball and then go with the fastball, and they made adjustments. It wasn't my day."
Center fielder Josh Hamilton also had a rough first inning, as two misplays allowed two extra runs to score. With one out and two runners on, Hamilton let a ground ball single by Josh Donaldson get past him. The Athletics got two runs and Donaldson ended up on third.
Perez struck out Josh Reddick, but Derek Norris followed with a line drive to left-center. Hamilton got to the ball, but it sailed above his glove and ended up going to the wall. Norris legged out an RBI triple and the Athletics had a 5-0 lead.
"The ball snakes here, everybody knows that," Hamilton said. "I got to where the ball was and put my glove down, but I peeked too early and the ball went around it. The ball in the gap ... I went to the spot where I thought the ball would be and it sailed on me."
Hamilton was also 0-for-4 with two strikeouts and 0-for-2 with runners in scoring position. The Rangers were 0-for-7 on the night in those situations and are 6-for-59 in the last 10 games. The Athletics were 8-for-22 with runners in scoring position on Wednesday.
"You don't like to have a game like that, but it happens," Hamilton said. "Personally, I'm not going to give up or put my head down, and our team is not going to do that."
Perez is scheduled to face the Athletics again on Monday in Oakland. If the Rangers haven't clinched a playoff spot by then, they'll have to decide whether to stay with Perez or go back to Feldman, who made an emergency start in place of Yu Darvish on Tuesday.
"I haven't had a chance to think about that yet," Washington said. "Perez just got too many balls up in the middle of the plate."
Perez, who allowed four runs in four innings in his last start against the Angels, is now 1-3 with a 5.03 ERA in six starts and six relief appearances during his time with the Rangers this season.
Rangers starters, with Darvish missing his Tuesday assignment because of a stiff neck, have pitched 7 2/3 innings in three games against the Athletics, allowing 10 runs on 14 hits and five walks.
That has resulted in 15 appearances by 12 Rangers relievers, including two each by Tanner Scheppers, Oswalt and Koji Uehara. The Rangers used Wilmer Font on Wednesday for only the second time since he was called up from Triple-A.
The Rangers trailed, 5-0, before coming to bat in the first inning against Athletics rookie Jarrod Parker. Elvis Andrus drove in a run with a double in the first and, after Oswalt put up a scoreless inning in relief, the Rangers scratched out two more in the second when Parker had trouble finding the strike zone.
That made it 5-3. But Font took over for Oswalt in the third and walked Josh Donaldson and Josh Reddick to start the inning.
"I was just hoping he would give us one inning," Washington said. "Oswalt gave us what he could, so I was hoping to get one inning out of him, get some more runs and get to the big part of our bullpen."
Scheppers came in but loaded the bases with a one-out walk to Cliff Pennington. Stephen Drew followed with a single to center to drive home two runs. Scheppers also gave up another run in the fourth before Tateyama took over.
"There was some padding, but with that team you never really feel that secure, and after a five-run lead it's a ballgame pretty quickly and Jarrod's throwing close to 60 pitches in two innings," Oakland manager Bob Melvin said. "So from that standpoint, he made a terrific recovery to go six innings, which we needed."