Walker drove in a career-high five runs as the Pirates crushed the Detroit Tigers 10-1 on Friday night.
He smacked a two-run double in the sixth off Detroit reliever Brayan Villarreal to help break open a tight game and later added a three-run homer in the ninth as the Pirates won their third straight, matching their longest winning streak of the season.
"We had it firing on all cylinders today," Walker said.
Particularly starter Jeff Karstens (3-2), who put together his best performance of the year. He retired the first 14 he faced and gave up just one run on three hits in six innings, striking out four without issuing a walk.
Karstens gave much of the credit to catcher Ryan Doumit, who made sure the right-hander kept the slumping Tigers from focusing on Karstens' relatively pedestrian fastball.
"We talked about it before the game [to] try and keep them off balance," Karstens said. "They're a pretty good fastball hitting team, especially [Miguel] Cabrera and [Victor] Martinez and just try to stay out of situations where they can hurt us."
Karstens made sure not to let his team's highest scoring game of the way go to waste. The Pirates had scored a grand total of six runs in his last four starts but put up six in the sixth inning alone after getting to Detroit's Brad Penny (4-4).
"Ten runs is always good," Karstens said.
Penny came in with wins in four of his last five starts, but surrendered five runs in 5 2/3 innings, thanks in part to a season-high five walks, as the Tigers lost their fourth in a row.
"Just too many walks and they got three infield hits off me," Penny said. "It just wasn't my night. I didn't pitch well enough to win."
The Pirates have been woeful against their American League counterparts since interleague play began in 1997, entering the series just 73-123 against the AL. Yet most of that damage has come on the road. They're now a respectable 51-51 at home after beating Detroit and manager Jim Leyland, who served as Pittsburgh's manager from 1986-96.
Leyland said before the game he's impressed with the foundation the Pirates have put in place. Pittsburgh hasn't had a winning season since Leyland guided them to the National League East title in 1992. The Pirates lost 105 games a year ago but have remained competitive so far this spring behind the play of a surprisingly consistent pitching staff.
The group includes Karstens, who started the year coming out of the bullpen, but was thrust into a starting role when Ross Ohlendorf went down with right shoulder injury.
Though Karstens hasn't been dominant, he has been effective. He stayed that way against the Tigers, who have struggled following a seven-game winning streak. They've lost four in a row, scoring six runs in the process.
"We're just not swinging the bats right now," Leyland said. "It's as simple as that. We need to start scoring runs. We've got to find a way to break out of this."
Detroit didn't get a baserunner until Brennan Boesch's two-out flare to center with two outs in the fifth. Karstens' only mistake of the night came on a fastball he left up in the zone while pitching to Ramon Santiago in the sixth. Santiago responded by depositing the pitch into the right-field seats for his first home run of the season to tie it at 1.
It didn't stay tied for long.
Lyle Overbay led off the bottom of the inning with a drive over the center-field wall, and then the Pirates -- who came in hitting just .236 on the season -- really went to work.
Penny did little to help himself. He came in having won four of his previous five starts, posting an ERA of 1.51 over that span, with six walks. He nearly matched that Friday, when 52 of his 105 pitches failed to hit the strike zone. Still, he managed to avoid any real trouble until the sixth.
Leyland wanted to bring in left-hander Brad Thomas, but his elbow locked up while he got loose, forcing Villarreal into action.
The right-handed Villarreal walked Jose Tabata to load the bases and Garrett Jones followed with a double to center that pushed the lead to 5-1. Walker then drilled a double of his own to left to give Pittsburgh more than enough breathing room.
"It put us in a little bit of bind," Leyland said. "I didn't feel real comfortable with Villarreal facing those guys. In the end, it was neither here nor there."
The Pirates gave third baseman Pedro Alvarez the day off after he tweaked his quadriceps, which forced him to sit out five games earlier in the month. ... Penny issued his first walk since May 3 when Ronny Cedeno earned a free pass in the bottom of the third, a span of 22 1/3 innings. ... Detroit's Austin Jackson extended his hitting streak to 12 -- the longest of his career -- with a double in the sixth. ... A crowd of 24,396 turned out, the second-highest attended weeknight game of the year.