Chris Robshaw and Mike Brown are both doubts for England’s Six Nations opener against Italy as Eddie Jones’s injury problems continue to worsen before the start of the championship.

Robshaw has missed Harlequins’ past two matches with a back injury while Brown was taken to hospital with blurred vision this month and has not been able to take part in contact work at England’s training camp in Portugal.

The absence of Robshaw would be a considerable blow for Jones, whose back-row numbers are already depleted with Billy Vunipola, Nathan Hughes, Tom Curry and James Haskell all unavailable through injury or suspension. It leaves Jones with Gary Graham, Sam Simmonds, Sam Underhill and Zach Mercer – who have six caps between them – as fit back-rowers with less than two weeks until the tournament begins, and as a result the Saracens lock Nick Isiekwe has been training as a flanker.

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Robshaw has been limited to fitness work in the swimming pool in Portugal and Jones said: “Chris Robshaw would win any sort of water Olympics at the moment. He’s unbelievable in the pool. He did a water aerobics class with a bunch of Portuguese women yesterday [Tuesday]. Apparently, he was the best in the class. If we play Italy in the pool he’d be all right, but if we’re playing rugby then he’d be borderline to get there.

“Mike Brown is starting to do some light skills today [Wednesday] and we’d be hopeful that by the middle of next week he’d be all right to train. He’s also borderline for Italy.”

Brown’s absence would be less disruptive for England with Anthony Watson able to step in at full-back, as he did during the autumn internationals but Jones’s problems in the back three have been made worse with Jack Nowell unlikely to be ready to face Italy with an ankle problem.

Jones also confirmed Nowell’s Exeter team-mate Henry Slade, who did not travel to Portugal because of a shoulder injury sustained last weekend, will be out of action for at least three weeks. He has, however, been boosted by the return to fitness of Ben Te’o in Portugal but Kyle Sinckler’s hamstring injury will rule him out for up to seven weeks, taking the number of England absentees to 18 if Brown and Robshaw do not recover in time for the trip to Rome.