The Portuguese winger spent much of his youth career at White Hart Lane before moving to Atvidabergs earlier this year.
The former Celtic manager took the 20-year-old in over the summer just a few months after the Portuguese youngster left White Hart Lane to sign for Swedish side Atvidabergs in the Allsvenskan.
And he caught the eye in a 0-0 draw with Nuneaton Town at the weekend.
“He’s got a good pedigree,” Mowbray is quoted as saying in the Telegraph. “He’s been at Tottenham Hotspur and is a very technical and talented footballer who you can tell he has got natural ability and a bit of flair.
“The question for Ruben, of course, is whether his physicality can deal with the first division because there are a lot of games in this league which are very hurley-burley at 100 miles per hour and you can see what type of footballer he is.
“He’s trained for a day or two and looked very impressive, I would have to say, but the only question in my mind is if we were to do anything with him would we have to pick the right games for him.
“Obviously he’s still only a young boy and very slight and yet we are all impressed with his talent, technique and positive play.
"There’s no reason why he can’t stay on our training ground for another week or two and make a decision when we need to.”
Lameiras never featured for Spurs, though did impress in the club's development squad, and he scored 4 times and assisted 4 in his half a year at Tottenham last season.
He arrived at the academy in 2011, and signed a professional contract in 2014 before moving to Sweden, where he made his first team debut, playing 11 times.
Mowbray is likely to give the winger more time to impress, with a contract offer a real possibility if he can convince that his natural ability outweighs his slight build.