Baker's shot in the second inning gave the Rangers the lead, but it was Berkman's fourth homer of the season into the left-field seats that broke the game open in the third and sent Saunders to his first career loss at Safeco Field. It was the first homer for Baker since May 10 and first for Berkman since May 11.
Saunders (3-5) entered the night 9-0 at Safeco Field, including a 3-0 mark with a 0.94 ERA this season. But Saunders gave up six earned runs and eight hits in just five innings and the Mariners lost their seventh straight.
Texas starter Justin Grimm (4-3) overcame a rough first few innings to pitch into the seventh despite giving up 10 hits. Grimm avoided a big inning, didn't walk a batter and struck out five in beating the Mariners for the second time this season.
Joe Nathan got his 15th save of the season getting Michael Morse for the final out of the game after Seattle scored twice and had two runners on in the ninth.
Grimm wasn't at his best early in the game as Seattle battered him for eight hits in the first 2 2-3 innings and there were relievers warming in the Rangers bullpen for many of the early inning. But Grimm managed to limit any major damage - helped by a blown call by first base umpire Jeff Nelson in the second - before settling down and retiring seven straight batters at one point.
Seattle's chance at a big second inning took a hit with a botched call by Nelson. Jesus Sucre hit a grounder to Mitch Moreland at first, who threw down to second to get the lead runner. The relay from Elvis Andrus back to first was in time to get Sucre but the throw was caught by Grimm running over to cover and not Moreland, whose foot was on the bag. Nelson missed that it was Grimm who caught the throw and called Sucre out.
Seattle manager Eric Wedge immediately came out to argue, but it was unclear if he had seen that Grimm caught the ball, not Moreland. Some of the furor stopped when Brendan Ryan followed with a two-out RBI double to tie the game at 2 and was further muted by what the Rangers did against Saunders and Seattle's bullpen.
Saunders had been fantastic at Safeco Field, having never lost at the Mariners home park heading into Friday night. In his previous 11 starts at the stadium, Saunders was 8-0 with a 0.94 ERA.
Saunders' problems started when he walked Nelson Cruz on a 3-2 pitch in the second inning and gave up Baker's opposite-field homer two batters later to give Texas a 2-1 lead. He immediately faced problems in the third giving up a leadoff single to Jurickson Profar and a one-out double to Moreland. After striking out Berkman looking in the first inning, Saunders got just one pitch into the at-bat his next time up. Berkman drove the first pitch out to left to give the Rangers a 5-2 lead.
Texas scored three more times in the seventh against Seattle's bullpen, capped by David Murphy's two-out, two-run single.
Notes: Seattle's been outscored 28-6 in the last three games. ... Texas manager Ron Washington said he has yet to settle on his starters for Monday's day-night doubleheader at Arizona. .... Raul Ibanez's had an RBI double in the third inning. It was the 400th double of his career. ... Injured Texas RHP Alexi Ogando (biceps tendinitis) will throw a bullpen session between games of the Rangers' doubleheader on Monday in Arizona. He'll be reassessed after the bullpen and could come off the disabled list next weekend.