A costly error helped the Mariners tie the game in the bottom of the 10th, and they went on to score a walkoff win on Willie Horton’s single in the 11th as Seattle downed the Royals, 4-3, on a Monday night at the Kingdome.

After the Royals scored an unearned run in the top of the 10th, they returned the favor in the bottom of the inning. Shortstop Onix Concepcion committed a throwing error on leadoff hitter Leon Roberts’ grounder. With one out, Larry Milbourne singled to move Roberts to third. Pinch-hitter Jerry Narron hit a sacrifice fly to tie the game at 3-3.

Seattle then scored with one out in the 11th. Bruce Bochte doubled with one out and scored when Horton hit a line drive back up the middle. Pitcher Dan Quisenberry got a glove on it, but the ball deflected into short right field and Bochte scored without a throw. It was not a blown save for Quisenberry as he had entered the game in the eighth with the Royals behind, but the American League’s saves leader did take his seventh loss of the year.

The Royals had been trying to come from behind all night. Seattle, after collecting two singles in the first off Royals starter Larry Gura but having both runners caught stealing, scored in the second. Reggie Walton doubled with two outs and scored on Marc Hill’s single.

The Mariners added an unearned run in the fourth as Juan Beniquez doubled with one out. Walton reached on an infield single, with Beniquez holding at second. Hill hit a grounder that was mishandled by George Brett at third base, allowing Beniquez to score and runners to reach second and third. Gura got out of the inning with no further damage, though, keeping the Seattle lead at 2-0.

Seattle starter Floyd Bannister held Kansas City to one hit through the first six innings. But John Wathan walked with one out in the seventh and Willie Aikens followed with his 19th home run of the year, tying the game at 2-2.

The tie didn’t last long, as Julio Cruz led off the seventh with a walk. After taking second on a bunt, Cruz scored on a Bochte single.

Brett led off the ninth with his 21st home run of the year, tying the score at 3-3. The Royals then took the lead in the top of the 10th. Jose Cardenal and Frank White started the inning with singles. Bannister retired the next two hitters but walked Brett to load the bases. Hal McRae hit a grounder to short that could have ended the inning, but Cruz was late covering second and Brett beat the throw. That allowed Cardenal to score the go-ahead run. With Quisenberry on the mound, it looked like the Royals would pull out a victory, but it wasn’t to be.

The loss dropped the Royals to 92-59 on the season. They still held a 16-game lead in the AL West.

George Brett watch: 1-4 with the home run. Brett was now in a 2-14 slump, although both hits were home runs. Season stats: .393/.458/.663

Box score and play-by-play: https://www.baseball-reference.com/boxes/SEA/SEA198009220.shtml

1980 news: The Iraqi air force bombed several targets in Iran as the two nations, after a few weeks of border skirmishes, began a war that would last almost eight years and result in some 500,000 casualties between the two countries.

Today’s birthdays: Bob Lemon (1920), Vince Coleman (1961), Mike Matheny (1970), Chris Ellis (1992)