The 38-year-old outfielder needs some help to recover after big games now.
Sanders drove in a season-high three runs and the Royals snapped a nine-game losing streak at Safeco Field. He also stole third and scored on a throwing error as the Royals (14-40) won by their second-highest margin of the season.
Kansas City, which won its first road day game this year, had 15 hits -- one more than it had in its previous three games combined when it scored a total of one run and lost three times.
"Haven't had one of these in a while -- if at all," Royals manager Buddy Bell said.
"From a total package standpoint, that's probably as good as we've played in a while."
Sanders hit a sacrifice fly in the third inning to drive in Tony Graffanino for a 3-2 lead. Ichiro Suzuki hauled in Sanders' flyball on the warning track in right field. It was the second time in the series that Sanders had come close to becoming the fifth major league player with 300 home runs and 300 stolen bases.
"I know. You guys keep bringing it up," Sanders said, laughing and rubbing beads of sweat off his shaved head.
Seattle tied it in the bottom of the third on Adrian Beltre's two-out double and Richie Sexson's RBI single. But Kansas City took the lead for good in the fourth on Angel Berroa's double and John Buck's two-run homer off erratic Jarrod Washburn (3-7).
Catcher Kenji Johjima's target on the full-count pitch to Buck was low and away. Washburn's 94 mph fastball was high and down the middle.
"You just can't pitch up in the big leagues," Mariners manager Mike Hargrove said.
In the fifth, Sanders hit a one-out single and advanced to second when Washburn walked Emil Brown, who homered in the second. Sanders then stole third and scored when Johjima's throw sailed into left field. Mark Teahen singled in Brown to make it 7-3.
Sanders added a two-run single in the sixth to increase the Kansas City lead to six. His previous high for a game this season was two RBI, accomplished on six different occasions.
"If you're 38 and to be that effective, that means you've had to have many good years before," Buck said. "He's our true leader. That's probably why he was handpicked to be here."
Former general manager Allard Baird, who was fired last week, signed Sanders out of St. Louis with a $10 million, two-year contract last winter. This is Sanders' eighth team -- and perhaps his toughest challenge at self-motivation.
"I knew when I signed it'd be a tough road," Sanders said. "I didn't know it would be this tough."
Washburn allowed a season-high seven runs to a team that had scored one run in its previous 28 innings. He yielded eight hits and two walks while striking out five in 4 1/3 innings. The runs were the most Washburn had allowed since May 8, 2005, at Detroit, when he was with the Angels.
He counted it as his worst Seattle outing, beyond allowing six runs in five innings against Cleveland on April 11.
Washburn has a 4.50 ERA and has won just once since April 26. Not exactly what Seattle was expecting when it signed him to a $37 million, four-year contract.
"I've been pitching pretty well for the most part this year," Washburn said. "In my opinion, I've really had two bad ones."
Kansas City's Mark Redman (1-4) allowed eight hits and four runs in 5 2/3 innings pitching the day before his 69-year-old father, Allen, has life-threatening surgery in San Diego. He walked three and struck out two while pitching for the first time since May 19. He was coming off the bereavement list.
"I knew he was there at the house watching -- he doesn't miss a game," Redman said of his father. "My mind's on him. I'm just trying to work through it."
Redman had gone 16 starts without a win before Sunday.
Elmer Dessens pitched the final 3 1/3 innings for his fourth career save and first in the AL.
Beltre hit a two-run homer in the first inning. It was his second homer in two games and his fourth of the season. He has eight hits in five games since moving from fifth to second in the batting order. Hargrove said Beltre may stay there for 10 to 20 games -- or all season. ... Teahen had his first two hits since being recalled from Triple-A Omaha on Saturday. ... LF Raul Ibanez did not play for the first time in 244 games because of what the Mariners called flulike symptoms. It was his first day off since Sept. 8, 2004. Suzuki holds the Seattle record with an ongoing games-played streak of 297.