Alberto Moreno is in doubt for Liverpool's Europa League meeting with Manchester United on Thursday.

The Spanish left-back sustained a hamstring injury in Wednesday's training session at Old Trafford and is now in danger of missing the Round of 16 second leg at Old Trafford.

Moreno, 23, was an integral part of Liverpool's 2-0 first leg win at Anfield last week but could now be replaced by 21-year-old Brad Smith, with Jon Flanagan ineligible for European games.

The Australian has made seven appearances under Klopp and last featured in the FA Cup loss to West Ham United in early February.