The 21-year-old was hurt as he fell awkwardly when delivering a cross during the first half of the second-leg tie.
Neymar was clearly in pain and unable to put weight on his injured leg as he was helped from the field by medical staff.
A subsequent update from Barcelona's official Twitter account confirmed Neymar's injury and revealed he will undergo further tests on Friday in a bid to establish the extent of the problem.
"Neymar sprained the peroneal tendon in his right ankle," read the tweet.
"He will undergo additional tests tomorrow (Friday)."
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