His RBI single with two outs in the 12th inning gave the Mariners a 5-4 victory Wednesday night over the A's.
"For the team, it was a good win," Sexson said. "Sometimes wins like these are good for the morale. When you're down and come back, and then battle back and win a game like this, it tends to get a team rolling."
Oakland took a 4-3 lead in the top of the 12th but the Mariners scored two unearned runs in their half of the inning.
With one out, Pat Borders singled off Ryan Glynn (0-4). Ichiro Suzuki hit a grounder that Glynn fielded, but shortstop Bobby Crosby did not handle the pitcher's throw for an error on a fielder's choice.
Randy Winn's single scored Borders from second to tie it and Sexson's third hit of the game scored Suzuki from second to end the game that lasted 3 hours, 59 minutes.
"I was just trying to get a single there, nothing more," Sexson said. "With Ichiro on second, that's pretty much all you've got to do. A lot of guys don't even score on that ball."
The A's have been in the AL West cellar since May 21. They had won four in a row against Seattle.
The Mariners welcomed back starting second baseman Bret Boone, who had a key sacrifice in the team's two-run ninth to tie the score at 3-all. Boone returned to the lineup after being benched for four games to work on his mechanical problems at the plate.
"We're going to give up runs and we're going to give up hits," said Guardado, who gave up his first run in 15 games. "But we came out on the winning side and you try to think always positive."
Seattle forced extra innings when rookie Mike Morse's two-run single with two outs in the ninth off Justin Duchscherer tied the game 3-3.
In the top of the 12th, Eric Chavez, who was 4-for-6 with two doubles, singled to center with one out off Guardado, the sixth Seattle pitcher. Chavez went to second on a groundout and stole third before Byrnes doubled down the right-field line.
It was the first run allowed by Guardado in 15 appearances.
Glynn, Oakland's sixth pitcher, worked two innings.
Oakland scored in the sixth on Chavez's double over the bag past sprawling third baseman Adrian Beltre. The A's made it 2-0 in the seventh when Byrnes tripled off the auxiliary scoreboard in left and rookie Dan Johnson hit a sacrifice fly.
Sexson led off Seattle's seventh with his 16th homer, a solo shot.
Oakland starter Barry Zito pitched 7 1/3 innings, giving up one run and four hits.
Seattle starter Jamie Moyer also went 7 1/3 innings, allowing three runs and eight hits.
- After being benched for four games to work on mechanics with hitting coach Don Baylor, Boone returned and went 1-for-4. Manager Mike Hargrove said Boone would stay in the lineup.
- The Mariners are 1-2 in extra inning games and the A's are 4-2.
- The Mariners won for the first time in 37 games when trailing after eight innings.
- The A's are 1-11 in one-run decisions on the road and 9-12 in one-run decisions overall.