"It's another muscle - it looks like, hopefully, only a little tear", he told reporters after the match.
"We will see, but we can not say anymore it now".
Set-pieces were probably the most positive thing today.
"Maybe tomorrow or the day after tomorrow we will know more, but in this moment we only know that it was too painful for him to carry on".
The game was very hard for both teams.
Here are five things we learned from the Jurgen Klopp derby in America.
This made for uncomfortable viewing as Liverpool fans bemoaned the German.
Netherlands' Virgil van Dijk opened the scoring for Liverpool in the 25th minute with a perfectly timed leaping header off a long cross from Andrew Robertson.
Pulisic won a 66th-minute penalty that he converted himself, then grabbed an 89th-minute victor by finishing off a flowing Dortmund counter-attack.
Liverpool went close to restoring their lead in the 77th minute as Dominic Solanke played in Alberto Moreno with a delightful pass, but the latter saw his effort tipped wide.
The match appeared to be heading towards a penalty shootout until Pulisic rounded off a counter-attack with a cool finish.
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.
"On a day like this you have to stay strong and show desire, greed to keep going".
Liverpool coach Jurgen Klopp has asked Belgian striker with Kenyan roots Divock Origi to prove himself or risk losing his place in the team in the coming season.
Liverpool goalkeeper Loris Karius is unhappy with the arrival of rival shot-stopper Alisson and is ready to push for a transfer away from Anfield this summer, according to reports.
Liverpool will fly to NY on Tuesday morning ahead of their second International Champions Cup game, when they will face Manchester City the following day.More news: New MacBook Pros are the most powerful laptops Apple has ever made