Lamela was one of seven players who were signed last summer by technical director Franco Baldini and former head coach Andre Villas-Boas.
But the former Roma man has been restricted to just 17 appearances in all competitions due to injuries and a lack of form.
Hip and back injuries have prevented Lamela from lining up for Spurs since the 3-0 win over Stoke in December and Sherwood has all but written off the Argentina international's chances of returning this season.
"He isn't fit to play," Sherwood said. "He's been unfortunate with injuries and it's a shame that he's picked up the knocks because taking the settling in period aside, how are you meant to settle when you can't go out there and perform because you've had this serious back injury?
"He's probably not going to play this season."
Lamela's World Cup place could also now be hanging in the balance due to his inactivity but Sherwood would have no qualms if Argentina coach Alejandro Sabella wanted to include the winger in his squad.
"Like I say, he's been out a very long time," he added.
"He's going to need a pre-season before he can play. It's up to their manager and if they think he needs to play any competitive games previous to that.
"I think it comes down to how sought after he is out there by the manager. He needs the games doesn't he? And next season he comes back in and he's in a better place."
Lamela may be the highest profile of Spurs' summer signings to find his first season a difficult one but he is not alone.
Roberto Soldado has scored just once since the turn of the year while Paulinho, Etienne Capoue and Nacer Chadli have shown only brief signs of their true potential.
None of those players had previous experience of English football before signing for Spurs and Sherwood feels that is something that worked against both the club and their new acquisitions.
He highlighted Everton's business, which saw them sign England midfielder Gareth Barry and Chelsea striker Romelu Lukaku on loan, as the perfect example of how to go about bringing in players to make a difference.
"I am a firm believer that Premier League experience is key," he added.
"Yes, you can buy someone who has never played in the Premier League and he comes over and he is a revelation but it's more of a risk doing that.
"If you want to look at any team you've got to look at Everton and what they've done in the transfer market - it is second to none.
"On Deadline Day they looked like an average side - all of a sudden they make three signings and it turns them into what they are now.
"That's the business that is done. It was very cute from [Roberto] Martinez and whoever was involved in bringing them in because whoever brought them in, certainly they were Martinez's players he wanted.
"You've got Gareth Barry with 534 games or whatever it is in the Premier League - crucial for any club. Lukaku was the best young player last season. He had that loan spell at Everton where he did brilliantly and he has it onto this year.
"And then there's Gerard Deulofeu who everyone knows is in development phase of football. He can be anything he possibly wants to be and he is showing that now, and the acquisition of McCarthy, they have certainly done brilliantly in the transfer market."