On the mound for the Rangers was left-hander Michael Kirkman, who struck out the left-handed Ortiz just two days earlier in his only official at-bat against him. Pedroia, who bats from the right side, was 1-for-1 with a double off Kirkman.
With Jonny Gomes on second base and nobody out, Pedroia was handed the free pass and Ortiz hammered the first pitch he saw, a fastball high-and-tight, over the right-field fence for a walk-off home run. The Red Sox won, 6-3.
"That was the best move to make right there," Washington said. "It was the only move to make. I could live with Papi doing that, but if I would have thrown to Pedroia and he would've won the game, I couldn't live with that."
Kirkman, who took his second loss of the season as his ERA rose to 8.18, said the plan was to get ahead of Ortiz with inside fastballs and then try to strike him out with a slider.
"I thought it was a really good pitch, movement inside, right where I wanted it," Kirkman said. "And he just got the barrel to it. Apparently he was sitting on that pitch."
Washington said he was limited with options out of the bullpen as lefty Neal Cotts threw 23 pitches Wednesday. Closer Joe Nathan was warming up, but managers don't often use their closer in a tie game on the road.
The Rangers still have faith in Kirkman, who has allowed runs in five of his last six appearances.
"He's still here, isn't he?" Washington said. "We put him out there tonight. That's my feeling. Confident that he can come in here and get it done. He's got to get confident in himself."
Nathan would've surely been in the game in the ninth had the Rangers turned a clean double play in the seventh to hold a 3-2 lead.
But Lance Berkman, playing first base in place of Mitch Moreland, who was placed on the 15-day disabled list with a right hamstring strain before the game, fielded a ball that took a late hop off the bat of Mike Napoli and couldn't make a clean throw to second.
Elvis Andrus had to bend down to scoop it before making a throw to first and Napoli beat the ball to the bag by a split-second as the tying run crossed home.
"I probably could've [nailed Jacoby Ellsbury at home]," Berkman said. "But the play there is to try to turn the double play because the ball was hit pretty hard. I make a decent throw, I think we turn it no problem. We almost turned it as it was."
For the most part, Berkman played a solid game at first, highlighted by a run-saving play in the fifth when he charged the line and gunned down Ellsbury -- who leads the American League with 21 stolen bases -- at home plate.
"He did well," said Washington, who will only use Berkman sparingly at first base in Moreland's absence as natural first baseman Chris McGuiness is the favored choice. "I wouldn't expect anything else out of Berkman. [The bad throw on the double play was] just one of those things. If the ball would've stayed clean, maybe things would've happened differently, but when the ball jumped on him, maybe he tried to rush a little bit and that's what caused it to be what it was."
The Sox left 10 runners on base, thanks in large part to Rangers' starter Derek Holland, who didn't have his best stuff, but made big pitches when he needed to, stranding baserunners in four of his six innings.
The Rangers allowed at least one baserunner in every inning.
"Going into it, I thought I had great stuff," said Holland, who allowed two runs on nine hits and three walks while tying a season-low with four strikeouts. "The thing that hurt me was falling behind on a lot of guys and the walks."
Pedroia went 1-for-3 off Holland, including a two-out, two-run double in the third, but Holland retired him two other times, each with two runners on base.
"He's a great hitter, but I battled out there," Holland said.
The Rangers plated a pair off Red Sox starter Jon Lester on a second-inning two-run blast by Jeff Baker, who continues to pummel left-handed pitching. He's 15-for-39 (.385) with six home runs against southpaws this season.
Adrian Beltre smashed a solo shot over the Monster in the third to put Texas on top, 3-0. Beltre finished 3-for-4 as he continued to torch his former club. He was 11-for-21 against the Red Sox this season.
The Rangers finish their season series with the Red Sox having taken four of six.
With Ortiz's game-winning blast, though, the Rangers lost their first series to the Red Sox after winning five straight.
"I don't know what the game plan was right there but that's not really the guy you want to go after in that situation," Lester said of pitching to Ortiz. "He's done it plenty of times before for us."