Moreno, who after much criticism since joining Liverpool was finally starting to give decent performances, stayed down after blocking a shot during Liverpool’s Champions League 7-0 demolishing of their Russian opponents.

According to The Sun, the Spaniard is now undergoing scans to determine the severity of his injury. James Milner was preferred at left-back last season, but in recent games it seems that manager Jurgen Klopp has finally put some trust behind Moreno’s performances.
The Spaniard has arguably done well to repay his manager’s faith this season, but Klopp will have to make a big decision about his understudy.

Left-back is not Milner’s favoured position, but there is a significant lack of suitable replacements in the squad with enough top-flight experience.
After Moreno’s substitution, the fact that Moreno walked off the pitch himself did nothing to dispel the Liverpool fans’ worry, as Moreno looked severely sadden by his injury, verging on tears as he left play.
Those celebrating Alberto Moreno's injury need to support another club. He has fought tooth and nail for Liverpool and you can see how much the badge means to him. He's hardly put a foot wrong this season and deserves our support. #LFC
— Liam Bekker (@LiamBekker) December 6, 2017
This would suggest that Moreno thinks it’s a pretty serious injury and Liverpool will have to dig deep to replace him in the line-up.
Whilst Klopp had to turn to Milner as a quick substitute on Wednesday, he will have worries for his selection at the weekend.
Klopp confirmed in the summer that Milner would no longer be considered as a full-back and would only be played in his natural central midfield position.
But whether Klopp will be forced to go back on his word in this weekend's Merseyside derby remains to be seen.