Bayer Leverkusen coach Xabi Alonso said Saturday's 3-2 loss to RB Leipzig, who came back from 2-0 down, was "not a good sign" for the reigning champions.

Last season's unbeaten league and cup winners Leverkusen lost their first Bundesliga match since May 2023, a run of 35 games.

Leverkusen looked on course for a comfortable win late in the first half with a two-goal lead, playing fluent football reminiscent of last year's title triumph.

Jeremie Frimpong and Alex Grimaldo scored late in the first half to give Leverkusen a 2-0 lead, but two goals from Lois Openda and one from Kevin Kampl turned the match for Leipzig.

"It's not a good sign," said Alonso. "We need to correct that and be better."

Alonso said Leverkusen "need to improve everything" but added "I saw a lot of positive things today.

"It's hard, it's bitter -- I don't think we deserved to lose today.

"We were ready to go again in the second half but we didn't have so much control. We have to accept the loss. It's hard, but it's football."

Leverkusen lost just one of 53 games in the 2023-24 season as they won the league and cup double, while going down to Atalanta in the Europa League final.

Leverkusen needed to come from behind to win the German Supercup in August, and gave away a two-goal lead in last week's Bundesliga opener at Borussia Moenchengladbach before coming back to win 3-2.