Exequiel Palacios scored in the fourth minute of injury time to earn Bundesliga leaders Bayer Leverkusen a 1-0 win at Augsburg on Saturday, keeping them four points clear of reigning champions Bayern Munich.
Bayern's 3-0 home victory over Hoffenheim on Friday turned up the heat on Leverkusen.
The visitors looked set to drop points for just the fourth time this season, but Argentinian World Cup winner Palacios controlled Alex Grimaldo's cross and fired past home goalkeeper Finn Dahmen with only a minute of added time remaining.
The goal may prove crucial in the title race as Leverkusen restored their lead atop the table, with second-placed Bayern having a game in hand.
An "emotional" Alonso admitted: "I jumped a little (when the goal went in)... Our boys had belief to keep going until the end.
"The goal wasn't lucky, it was a reward for our good work in the game...
"But it's only one win, we need to keep going."
On the first weekend of fixtures since Franz Beckenbauer died aged 78, each match began after a moment's silence and a tribute to the German football legend.
Leverkusen looked slick early, carving out several chances as they dominated possession, but lacked the final killer blow without injured striker Victor Boniface.
Augsburg looked to have taken the lead through Phillip Tietz with 20 minutes remaining, but the striker's goal was ruled out for offside and Palacios had the final say.
Leipzig lose at home
Elsewhere, Eintracht Frankfurt won 1-0 at RB Leipzig to leapfrog Borussia Dortmund into fifth place.
Frankfurt took the lead just seven minutes in, Ansgar Knauff slamming a brilliant curling pass from Niels Nkounkou into the net.
Leipzig pushed for an equaliser but Frankfurt held on, consigning the German Cup holders to their first home league loss of the season.
Union Berlin held Freiburg to a goalless draw, continuing their solid if unspectacular form under new coach Nenad Bjelica.
Union had lost nine league games in a row prior to the Croat's arrival, but have now lost just one in four to move three points clear of the relegation play-off place.
Cologne missed a chance to move out of the automatic relegation zone, conceding a second-half goal to draw 1-1 with promoted Heidenheim.
Strugglers Mainz fought from a goal down to draw 1-1 at home with Wolfsburg, picking up a valuable point to keep them in 16th, the play-off spot.
Later on Saturday, Borussia Dortmund can take advantage of Leipzig's loss by moving to within three points of fourth place with a win at last-placed Darmstadt.
England winger Jadon Sancho could play for the visitors for the first time since 2021, having been named on the bench following his return on a six-month loan from Manchester United.
