Lang, who Galatasaray said would undergo surgery on the injury, had been introduced as a half-time substitute for Victor Osimhen after the Nigerian striker had hurt his wrist in an early challenge.
The substitute forward suffered a nasty injury of his own, though, after tumbling awkwardly beyond the Liverpool goal and appearing to slice his thumb on the advertising board.
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Lang immediately went down in discomfort after attempting to stabilise himself with his right hand, with a number of home players attending to him before medics rushed over to help out.
Galatasaray were forced to bring on the experienced Mauro Icardi as their second replacement up front, with Lang taken away on a stretcher after a period of treatment.
He was given warm applause from around the ground, with no Galatasaray fans in attendance due to a ban on visiting supporters.
Providing an update on both players, Galatasaray said: “In the first half of our away match against Liverpool in the Champions League Round of 16 second leg, our player Victor Osimhen took a blow to his arm and completed the first half, but following checks at half-time, he was not played in the second half due to the risk of a fracture in his arm.
Officials inspect advertising hoarding where Galatasaray’s Noa Lang hurt his thumb.
“After the match, under the supervision of our medical team, examinations at the hospital revealed a fracture in our player’s right forearm, and it was casted. A decision regarding surgery will be made in the coming days following further evaluations.
“In the second half of the same match, our player Noa Lang, who suffered an injury, sustained a serious cut to his right thumb, and it is planned for him to undergo surgery in Liverpool in the coming hours with the participation of our medical team.”
The Turkish side had taken a 1-0 lead into the second leg at Anfield after an impressive performance in Istanbul, but found themselves blown away in the second half to exit the competition.
Liverpool have set up a quarter-final tie with Paris Saint-Germain – the side that knocked them out of last year’s Champions League.