Alex Oxlade-Chamberlain is now a major doubt to play in a potential Champions League final and feature at World Cup 2018 for England having picked up a "really bad" knee injury in Liverpool's 5-2 win over Roma.
The England midfielder has been in fine form for the Reds in recent weeks, playing a huge part in their march to the last four, but he lasted barely 15 minutes on Tuesday before being forced to withdraw through injury.
Oxlade-Chamberlain dived into a challenge with Roma's Aleksandar Kolarov early in the first leg, and was left crumped on the floor with apparent damage to his knee.
Liverpool at first hesitated over calling for a substitution, but it quickly became evident that the former Arsenal man would play no further part in the encounter.
Klopp didn't hide his concern at full-time that the attacking midfielder, 24, could be sidelined for a while if the club's fears are verified by their medical team.
"Oxlade-Chamberlain is probably a really bad injury," Jurgen Klopp told BT Sport. "That is bad news for us. The squad doesn't get bigger at the moment so we need to be creative in the next few games."
Georginio Wijnaldum was the man chosen to replace Oxlade-Chamberlain with the scoreline poised at 0-0, although a shower of Liverpool goals gave the hosts a healthy 5-2 lead heading into the second leg at the Stadio Olimpico next Wednesday.
Liverpool will now have to wait for official confirmation on the severity of the their star's injury, with the second leg and a potential final now looking like they will have to be tackled without the former Arsenal star.
Gareth Southgate's England team was likely to have included Oxlade-Chamberlain, too, and the manager's final 23-man squad will surely need a replacement unless his knee injury is less serious than anticipated.