Monday's (AEST) LaLiga results – including Celta Vigo's shock win at Camp Nou – mean Barcelona can no longer win the title, with the club and Ter Stegen subsequently deciding to cut his season short.
A brief statement released by the club revealed Ter Stegen will "undergo a therapeutic procedure on the patellar tendon in his right knee on Thursday May 20 in Malmo by Dr Hakan Alfredson and under the supervision of the club's medial services".
While Barca did not outline a return date, Ter Stegen provided an update on his official Instagram account on Monday, confirming it means he will play no part at the delayed Euro 2020.
"I'm disappointed about yesterday's defeat and that now we can no longer win La Liga," he wrote.
"After a complicated start to the season, we showed good character going 19 matches unbeaten – but we weren't able to keep this form.
"I have decided together with the medical team of the club that I will do a complementary intervention on my knee.
"I'm sad that I will miss Euro 2020 this summer with Germany. For the first time in many years I will be a fan at home supporting my country, I hope we win it!
"After the summer break, when we are back on the pitch I hope to be able to play with fans [in attendance] once again, I miss it!
"Thank you for your support throughout a difficult season and stay healthy!"
Ter Stegen has featured 31 times in the league in 2020-21 for Barcelona, but his overall performance for the season has not been quite up to the high standards he has set previously.
He has conceded 32 goals from shots on target worth 29.07 expected goals on target (xGOT), meaning he has let in nearly three goals more than expected. Celta's first goal on Sunday came from a speculative Santi Mina shot worth just 0.04 xGOT.
Ter Stegen's xGOT differential of -2.93 this term is by far his worst across a single season at the club. In 2015-16, it was -1.44, though he only played seven LaLiga matches, while his next worst was -0.16 in 2019-20, a narrow margin which essentially meant he conceded as many goals as would be expected given the quality of the shots on target he faced.
But for this procedure the ex-Borussia Monchengladbach man certainly would have been a part of the Germany squad next month, though he would have been playing back-up to Bayern Munich's Manuel Neuer.
While Ter Stegen has let in more goals than he should have this season, Neuer has conceded 40 times in the Bundesliga from an xGOT value of 42.09, therefore preventing two goals in 2020-2021.
The Neuer or Ter Stegen debate has been a hot topic for Germany for a while now, though the data suggests that, at least this season, the Bayern star remains the safer option between the posts.