1990 American League Championship Series

Oakland won the series, 4–0.

Saturday, October 6, 1990, at Fenway Park in Boston, Massachusetts

The opening game of the series saw a battle of aces, as Oakland sent Dave Stewart to the hill against Boston's Roger Clemens. The game was a scoreless pitchers' duel until the bottom of the fourth, when Red Sox third baseman Wade Boggs launched a home run off Stewart. Despite mounting scoring threats in each of the next two innings, the Athletics failed to deliver against the "Rocket."

The shot by Boggs turned out to be the only home run in the 1990 ALCS.

Oakland finally came through in the seventh, when Larry Andersen replaced Clemens on the mound. Andersen walked Mark McGwire, who then was forced out at second by the next batter, Walt Weiss. A single by pinch-hitter Jamie Quirk moved Weiss to third, and he came home on a sacrifice fly by Rickey Henderson. In the eighth, the A's took the lead via small ball, as José Canseco singled, was sacrificed over to second by Harold Baines, stole third, and then plated on a single by Carney Lansford.

In the ninth, the wheels came off for the Red Sox bullpen, as Oakland blew the game wide open by erupting for seven runs, a historic distinction done only twice before in the postseason and the first in twenty years. [5] Henderson led the way with a two-run single and a stolen base, Terry Steinbach and Willie Randolph added RBI base hits, and Canseco chipped in with a sacrifice fly. With the game now far from a save situation, A's closer Dennis Eckersley shut Boston down in the bottom half of the inning. giving Oakland a 9–1 victory and a 1–0 series lead.

Sunday, October 7, 1990, at Fenway Park in Boston, Massachusetts

Game 2 saw the A's Bob Welch, the eventual 1990 American League Cy Young Award winner, take on Boston's Dana Kiecker. The Red Sox struck against Welch in the third, as Luis Rivera doubled, took third on a Jody Reed grounder, and scored on a sacrifice fly by Carlos Quintana. Oakland got the run back the very next half-inning, however, as Willie McGee doubled and scored on a single by Baines.

In the sixth, Boston manager Joe Morgan pulled Kiecker in favour of the bullpen, and as they had in Game 1, the A's went to work. Mike Gallego and Rickey Henderson ripped consecutive singles, and McGee forced Henderson, moving Gallego to third. He came home on a groundout by Baines, giving the A's a 2–1 advantage. In the ninth, the Athletics extended their lead to three runs, courtesy of an RBI double by Baines and a run-scoring single by McGwire. Eckersley worked a 1–2–3 ninth to secure his first save of the series, and Oakland carried a 2–0 ALCS lead back to the Coliseum.

Tuesday, October 9, 1990, at Oakland-Alameda County Coliseum in Oakland, California

For Game 3 in Oakland, the Red Sox threw Mike Boddicker, who had been the 1983 ALCS MVP with the Baltimore Orioles, against the Athletics' Mike Moore. In the second, the Red Sox drew first blood when Mike Greenwell walked, moved up to third on a single by Dwight Evans, and came home on a sacrifice fly by Tom Brunansky. Boston continued to lead until the bottom of the fourth, when the A's struck for two runs. Canseco and Baines both got on base and then executed a double steal, enabling Canseco to subsequently score on a Dave Henderson sacrifice fly and Baines to eventually plate on a single by Randolph.

In the sixth, Oakland added a pair of runs to their lead thanks to some shoddy fielding by the Red Sox. An error by Rivera on a ground ball allowed Baines to reach base, take second on a fly out by McGwire, then move to third when Dave Henderson was forced out by Steinbach. An RBI single by Randolph scored Baines and moved Steinbach to third. Steinbach then boldly tried to steal home and was gunned down, but an error by his Boston counterpart Tony Peña resulted in another run. In the ninth, Eckersley picked up his second save as the A's took a 3–0 stranglehold on the series.

Wednesday, October 10, 1990, at Oakland-Alameda County Coliseum in Oakland, California

The fourth game was a pitching rematch of Game 1, as Stewart again faced Clemens. In the bottom of the second, the "Rocket" gave up consecutive singles to Lansford and Steinbach, and both advanced one base due to a throwing error by Greenwell. McGwire then forced Steinbach, driving in Lansford with the first run of the game.

Randolph was the next batter, and when home plate umpire Terry Cooney adjudged Clemens' fifth pitch to him to be ball four, the Red Sox ace lost his composure, letting loose a stream of profanities. Although Clemens later claimed he was talking to his glove, Cooney assumed the comments were directed at him and promptly ejected Clemens from the game. Video evidence posted on YouTube shows Clemens looking at and talking directly to Cooney.[6] Boston manager Joe Morgan and Clemens fiercely argued the call. The Red Sox bench also exploded, with Clemens' indignant teammates hurling water coolers and litter onto the field. In the end, Clemens and Marty Barrett were thrown out; an angry Barrett had merited his ejection by throwing things onto the field.[7]

The ejection proved to be the turning point of the game, as Gallego proceeded to belt a double to center field off Clemens' replacement, Tom Bolton, scoring both McGwire and Randolph. The Red Sox briefly mounted a last-ditch rally in the top of the ninth, scoring a single run courtesy of an Ellis Burks double and a single by Jody Reed, but Athletics reliever Rick Honeycutt got Greenwell to ground out, handing Oakland its third straight American League pennant. This is Oakland's most recent pennant to date. This was Oakland's last postseason series win until 2006.