Liverpool’s pursuit of the Europa League title has been dealt a severe blow with Divock Origi expected to be sidelined for four to six weeks with ankle ligament damage.

The in-form Belgium international, who scored his 10th goal of the season in Wednesday’s derby defeat of Everton, was carried off at Anfield as a result of an appalling foul by Ramiro Funes Mori.

Fears that Origi had suffered a broken ankle were allayed by Jürgen Klopp after the 4-0 win. However, following a scan on Thursday, Liverpool fear the striker has suffered ligament damage that will rule the 21-year-old out for at least a month.

That will, in effect, mean Origi missing the rest of the season – along with recent Liverpool casualties Emre Can and Jordan Henderson – and damage the game plan that Klopp has employed in recent Europa League fixtures.

The Liverpool manager, who said Origi’s injury had cast a “big shadow” over the derby victory, is expected to confirm the extent of the injury on Friday.

Funes Mori apologised to Origi after becoming the first player sent off in a Merseyside derby for five years when he stamped on Origi’s ankle early in the second half at Anfield. Funes Mori’s recklessness led to Everton’s 10 men ultimately succumbing to a heavy defeat and Roberto Martínez losing the £9.5m defender for Saturday’s FA Cup semi-final against Manchester United.

In a statement published on social media, the Everton defender said: “I very much regret what happened yesterday. It was never my intention to harm a rival nor my colleagues leaving the field. And regarding Divock Origi, I fervently hope it’s nothing serious and know that was never my intention to hurt. I ask my apologies for what happened.”

Martínez is facing an anxious wait on his defensive options for the semi-final. Funes Mori will commence a three-match ban on Saturday, John Stones was forced out of the derby with stomach cramps, Phil Jagielka is recovering from a hamstring strain and Seamus Coleman is almost certainly out with a similar injury.

Stones was involved in training on Thursday and should be available for Wembley. Everton’s captain, Jagielka, has not been ruled out but Gareth Barry is expected to miss the semi-final with a groin injury that forced his withdrawal at half-time against Liverpool. Matthew Pennington will be recalled from a loan spell at Walsall to increase Martínez’s defensive options.