Borussia Dortmund have accused Sporting Lisbon of showing a lack of sportsmanship following the Bundesliga side's 2-1 win at the Estadio Jose Alvalade on Tuesday night.
As Sporting pushed for a late equaliser in Tuesday's Champions League clash, they declined to return the ball on two occasions in quick succession after Dortmund players had put the ball out of play to allow an injured teammates to receive treatment.
"I've never experienced bad sportsmanship like this in 30 years," BVB's sporting director Michael Zorc, a 1997 Champions League winner, told reporters. "It was one big disgrace. They twice did not return the ball despite us being down injured. That was not fair play."
The first incident, on 85 minutes, saw Dortmund defender Sokratis Papastathopoulos go down following a tackle before Sporting went on the attack. BVB keeper Roman Burki then claimed the ball from a cross and sent the ball out of play, with Sokratis getting up and Sporting not returning possession from the throw-in.
Moments later, Sporting striker Bas Dost knocked Sokratis into Burki's path, prompting a clash that left the defender bleeding. Burki again sent the ball out of play but Sporting played on.
The Laws of the Game state that the referee should allow "play to continue until the ball is out of play if a player is only slightly injured" and is only obliged to stop play in the case of a serious issue, particularly when there is any suspicion of a head injury, but it remains common practice for players to put the ball out for a throw-in when a member of either side remains on the floor with a clear problem.
In such cases, the team awarded the throw-in is expected to return possession.
Burki, who played a key role in preserving the visitors' lead during the run-in, said Sporting "tried to score the equaliser by any means necessary."
He added: "When I clear the ball because one of our players is injured and they just play on, it has nothing to do with respect."
Dortmund currently lead Real Madrid in Champions League Group F on goal difference after taking seven points from their opening three games. Sporting have three points and are third in the table ahead of their game at Dortmund on Nov. 2.