"It's another muscle - it looks like, hopefully, only a little tear", the manager told liverpoolfc.com at a post-match press conference.
Of course, this is not ideal for me, but I can not say much more about it. It is of course the most negative thing about the day.
"I know people think highly of him". But for that to happen we need a strong squad around him and Loris is an outstanding goalkeeper.
Speaking to reporters after the game, Klopp offered his insight into where Keïta might play next season and his thoughts on Daniel Sturridge's impressive form.
This made for uncomfortable viewing as Liverpool fans bemoaned the German.
Virgil van Dijk scored the only goal of an uneventful first half to send Liverpool into the break with the lead, but a string of half-time changes resulted in more action and ultimately saw Dortmund come from behind to win.
Watch: Christian Pulisic scores twice, sets up another vs. Liverpool
The talented Dortmund man then took a picture with the youngster and in return, made his day with a wonderful gesture.
Three minutes into injury time and the Bundesliga side snatched their third, this time off the right foot of Jacob Bruun Larsen at point-blank range.
Liverpool star Mohamed Salah sat out of the defeat, having only returned from holiday on Friday, but observed from the sideline at Bank of America Stadium alongside Sadio Mane.
"We have to learn from it, that's how it is, and then we have to go again". Whatever it is that's happening in your life to hold this much anger and hate, I pray that it passes and good things come to you.
Liverpool will aim to bounce back when they play Manchester City in New Jersey on Wednesday night, while Dortmund face Benfica in Pittsburgh, in Pulisic's home state of Pennsylvania.