Borussia Dortmund head coach Thomas Tuchel has hit out at what he perceived to be an overly physical approach from Bayer Leverkusen in Saturday's 2-0 defeat.
Bayern Munich's 1-1 draw against Cologne earlier in the day left Dortmund with the chance to close the gap on the Bundesliga leaders to one point at the Bay Arena.
However, goals in either half from Admir Mehmedi and Javier Hernandez consigned Dortmund to a second league defeat of the campaign.
To compound matters, Dortmund lost Gonzalo Castro and Sebastian Rode to injury and Tuchel suggested Leverkusen were lucky to finish the match with 11 men.
"We again [had] 21 fouls [in our favour]," Tuchel told Sky.
"We had to make substitutions due to injury. Castro and Rode were both unable to play on.
"We have to cope with a lot, our attacking players get fouled a lot. Boundaries have been crossed.
"Normally, a team would not end with 11 players if so many fouls are made throughout the game."
Dortmund have dropped to third place in the Bundesliga table following Saturday's defeat and are now trailing leaders Bayern Munich by four points.