The Welsh midfielder looked to have picked up a hamstring injury half an hour into the 1-0 win at the Stadio San Paolo after a high tackle on Napoli’s Piotr Zielinski.
“It is a muscular injury. Normally it will be some weeks out for him. But we have other players and we can find a performance and rotate players,” Arsenal manager Unai Emery told BT Sport.
Emery, whose side beat Napoli 3-0 on aggregate to set up a last-four clash with Valencia, said he didn’t know whether Ramsey would play again this season.
Ramsey, out of contract with Arsenal in June, will end an 11-year association with the Gunners after agreeing a deal with Juve reportedly worth £400,000 ($515,000) per week over four seasons.
Reduced to a bit-part player under Emery, Ramsey’s recent form – he has three goals in his last seven starts – had helped him regain a regular spot in the Arsenal side.
The 28-year-old, set to follow in the footsteps of countrymen John Charles and Ian Rush by switching England for Turin, had struck the opening goal in last week’s 2-0 win over Napoli.