LONDON: Liverpool manager Juergen Klopp is confident defender Virgil van Dijk will come back stronger as the Dutchman undergoes knee surgery and faces a battle to play again this season. The Premier League champions said on Sunday that Van Dijk has damaged knee ligaments following a challenge by Everton goalkeeper Jordan Pickford during Saturday's Merseyside derby at Goodison Park. Van Dijk's knee operation has yet to be scheduled and Klopp did not put a timescale on the centre back's return. 'A few things are clear... he now will be out for a while,' Klopp told Liverpool's website. 'I expected it pretty much on Saturday after the game immediately, especially when I saw the challenge back. 'These situations are absolutely rubbish. You don't need it but you have to get over it and Virgil will get over it, 100%, and today is already the first day, if you want, of the recovery. 'We are in contact. We are there for him, he knows that and we will wait for him like a good wife is waiting when the husband is in jail.' Pickford will not face retrospective action over his challenge after the Football Association determined the incident was seen at the time by the match officials, including VAR. Klopp said midfielder Naby Keita could feature in Wednesday's Champions League match at Ajax Amsterdam after he resumed training following a negative COVID-19 result. The 25-year-old had tested positive for the virus while on international duty with Guinea. Thiago Alcantara will undergo a fitness test ahead of the trip to Amsterdam following a late challenge on the Spanish midfielder by Richarlison, which led to the Brazilian being sent off in the 90th minute. 'He got a knock, a proper knock,' said the German boss. 'It's not even close to being as serious (as Van Dijk). But will he be ready for Wednesday? I don't know yet. We will see.'