Ter Stegen has played a key role in Barca's La Liga title defence, making 35 appearances and displaying consistently excellent form.
Coach Ernesto Valverde has rested the German in recent weeks around the Champions League semi-finals and ahead of the Copa showdown with Valencia on May 25, allowing Jasper Cillessen to step in for league games against Celta Vigo and Getafe.
However, Ter Stegen has still managed to sustain an injury, with Barca revealing on Thursday the 27-year-old is struggling with discomfort in his right knee.
The club have not given any further details regarding the severity of the injury, but Ter Stegen is likely at least to miss the trip to Eibar on Sunday and is a doubt for the showdown with Valencia in nine days' time.
[❗ BREAKING NEWS]— FC Barcelona (@FCBarcelona) May 16, 2019
Ter Stegen is having trouble with his right knee. He is out of action and his availability will depend on how things develop pic.twitter.com/gUEBKMDnUN
Valverde's side have already sealed a second successive La Liga title and will be looking to complete a domestic double at the Benito Villamarín Stadium in just over a week's time.
Barca fell to a shock Champions League semi-final defeat against Liverpool on May 7, losing 4-0 at Anfield and exiting the competition 4-3 on aggregate.
The Blaugrana managed to bounce back from that disappointment with a 2-0 win over Getafe five days later and will finally lift the league trophy this weekend, having wrapped up the title back in April.
Ter Stegen has been a fixture in Valverde's starting XI throughout the season and his loss represents a major blow for the Spaniard heading into a major final, but Cillessen has proved himself as an able deputy.
The Dutchman has appeared in nine matches across all competitions in total this season and currently serves as number one for the Netherlands at international level.