UPDATE 1-Soccer-Scintillating Dortmund muscle past champions Bayern 3-2
In a hugely entertaining encounter that lived up to its big-game billing, Dortmund came out on top, earning Bundesliga bragging rights and pulling away from their main title contenders going into the international break.
Robert Lewandowski twice put visitors Bayern ahead only for Dortmund captain Marco Reus to equalise each time before Spaniard Alcacer confirmed his 'super-sub' status in the 73rd minute with the decisive goal on the break.
It was Alcacer's seventh goal in his fourth substitute appearance this season and lifts Dortmund, who remain unbeaten in the league, to 27 points, with Borussia Moenchengladbach second on 24 and Bayern third on 20.
"We paid for the mistakes we made after a decent first half. We struggled with their speed when they charged our backline," said Bayern captain Manuel Neuer.
"We can all read the standings. It was not a bad performance from us but we lacked the cleverness to get a win here, which was possible."
Bayern's second league loss of the season also piles more pressure on embattled Bayern coach Niko Kovac, with the Bavarians, so accustomed to domestic success having won the last six league titles, now struggling in their pursuit of vibrant Dortmund.
They could drop to fourth on Sunday if RB Leipzig beat Bayer Leverkusen.
Yet it all started well for the champions, who took advantage of the home side's somewhat sluggish start, to take the lead with former Dortmund striker Lewandowski's 26th minute header.
Reus, in sensational form this season, was brought down in the box and drew the hosts level with his penalty four minutes after the restart.
Yet the joy of the home crowd was short-lived when Lewandowski again headed in at the far post after a quick combination for his 12th goal in nine games against his former club.
The hosts then laid siege to the Bayern box, with Reus wasting several golden chances before making amends with his eighth goal of the season, an unstoppable one-touch missile that left keeper Neuer frozen to the spot.
There was more misery to come for the visitors, who looked rattled by Dortmund's speed, as Spaniard Alcacer, beating the offside trap, raced clear to chip the ball over Neuer for the winner.
The Spaniard needed just 218 minutes to score eight league goals, seven of which have come as a substitute. No player has ever taken less time on the pitch to score his first eight goals in the Bundesliga.
Earlier, Gladbach tightened their hold on second place with as 3-1 victory at Werder Bremen courtesy of a hat-trick from forward Alassane Plea, who also took his season's tally to eight goals. (Reporting by Karolos Grohmann Editing by Ian Chadband)
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