Erik Lamela is out for a further six weeks with an injury setback, as his first season in English football goes from bad to worse. The Tottenham Hotspur record signing has damaged his back, as a result of overcompensating to protect the thigh injury that has kept him out since the turn of the year and, although the club expect him to return before the end of the season, the prognosis was grim.

Tim Sherwood, the manager, said it would be "weeks" before Lamela could play again and it is understood he meant at least six. Sherwood added that the Argentina winger, whose last appearance was as a substitute in the Premier League win over Stoke City on 29 December, would remain in England for his rehabilitation.

Lamela cost £30m last summer when he followed the sporting director, Franco Baldini, from Roma to Tottenham but he has struggled to adapt, both on and off the field, where he has so far failed to learn the language. The 21-year-old has been picked to start only three times in the league and his one goal for the club came in the Europa League group phase win over FC Sheriff.

Lamela was desperate for a loan move last month to reignite his career, particularly with the World Cup finals in mind, and there were several clubs in Serie A that wanted him. But Tottenham felt that they could not go from paying such a massive fee for a player to loaning him out only five months later.

"Lamela had a thigh strain and he was over-compensating for that, so now he has got a problem in his back, which we are assessing and we are not too confident," Sherwood said. "It will be weeks.

"It is difficult to adapt to a different country, a different league and a different language but, when you are suffering all these niggles and something more than minor at the moment, it is disappointing for the lad.

"But we signed him for the long term and we are sure that, in the end, he will come good for Tottenham and be a crowd favourite here. We are all big fans of him when we see him in training. It is just difficult to adjust to a different style of play and a different language. I'm sure Erik will pick it up. By the time he is fit, he will be fluent."

Sherwood will also be without the defender Vlad Chiriches and the midfielders Sandro and Gylfi Sigurdsson for Wednesday night's trip to Newcastle United. "Chiriches has a back injury that is quite similar to what Erik has got but Sandro is a bit closer," Sherwood said. "He is feeling more comfortable with his calf injury. Sigurdsson has a calf, too."

Sherwood shrugged off the comments of the Arsenal striker Olivier Giroud, who said that he had tried to get the Tottenham goalkeeper Hugo Lloris, his friend and France team-mate, to join him at the Emirates Stadium. Giroud said that Lloris was up for the switch.

"It doesn't annoy me," Sherwood said. "It would annoy his goalie at Arsenal [Wojciech Szczesny], you would have thought."