The assistant referee who was accidentally hit in the face by the ball during the Bundesliga match between VfL Wolfsburg and Cologne has been taken to a hospital after the incident on Saturday.
"He's doing well under the circumstances. He's been taken to hospital and will probably have to stay there overnight for observation," referee Sören Storks told broadcasters Sky.
Assistant referee Thorben Siewer was unintentionally hit in the face by a ball in the 14th minute of the match after it was kicked out of bounds by Cologne defender Max Finkgräfe.
"I would like to wish the assistant referee all the best. I hope he recovers quickly," Cologne coach Timo Schultz said. "I saw him on the way to the referee's booth. He couldn't really look straight ahead."
The match was interrupted for some 15 minutes as Siewer received medical care on the sidelines and had to be replaced by fourth official Nicolas Winter.
Winter's replacement was found in an unusual way: The stadium announcer asked for someone in the audience who had a referee's licence. Former Wolfsburg youth player Tobias Krull, who at the age of 32 is a goalkeeper and sporting director at neighbouring club MTV Gifhorn in the regional football league, then came forward.
"Tobias did a great job and helped out very, very well. A great performance. There is a fixed plan. We look for someone in the stadium who has a valid referee licence," Storks explained.
Referee spokesman Alex Feuerherdt added: "If there was no referee in the stadium, the game would have continued without a fourth official."