Chelsea may have to confront Rubin Kazan in the Europa League quarter-final without a recognised senior left-back after Ryan Bertrand was unable to take part in training after succumbing to a virus.

The England defender, who is first-choice at present with Ashley Cole still hamstrung, missed Tuesday's session and stayed away from Cobham. Bertrand will be assessed by the club's medical staff early on Wednesday and is expected to join the travelling squad who fly from Gatwick to Moscow mid-morning, but he will continue to be monitored right up to kick-off against Rubin on Thursday night as Chelsea defend a 3-1 first-leg lead.

Juan Mata had to be omitted from the recent game against Southampton with a virus but, with Cole expected to be absent for up to a further fortnight, the interim first-team manager, Rafael Benítez, would be left with only the young Dutchman Nathan Aké, 18, as a natural left-sided defender for the game at the Luzhniki stadium. The little-used Paulo Ferreira, who has filled in at times in the past, is a more experienced alternative. "The last thing I did [after training] was talk with the doctor on the pitch and I was asking her about Ryan," said Benítez. "She said he would report [on Wednesday] and we will decide. Anyway we will put him on the list and we will see."

Cole was able to use an exercise bike on Tuesday as he steps up his recovery from the hamstring injury sustained in last week's FA Cup quarter-final victory over Manchester United. Benítez spoke to him and another absentee, the centre-back Gary Cahill, prior to training. The latter has undergone minor arthroscopic surgery to shave the meniscus on the knee he damaged in last month's win against West Ham and will be out for around two weeks after that procedure was carried out nine days ago. "He'd come in to train on the Saturday we played Southampton and we tested him then, but he was not feeling so well so we did the operation quickly on the meniscus," said Benítez. "He had a small piece [shaved off]. He and Ashley are both doing well, but the main thing is to see how they react when they come back on to the pitch and start running. Then we will see how quickly they progress."

The Senegalese forward, Demba Ba, is cup-tied for the game against Rubin and will not travel to Moscow as he continues his own recovery from the ankle injury sustained in Sunday's win over Sunderland. He did not train on Tuesday. Chelsea are keen to ensure the 27-year-old is fully recovered before they face Manchester City in the FA Cup semi-final at Wembley on Sunday. Otherwise Fernando Torres will be the only fit senior forward in the first-team squad. "Demba did not train, just as a precaution, but it's not too serious," added Benítez. "He will not go to Moscow. Hopefully he can train here and be okay for the weekend."