The 22-year-old German, who joined Spurs for a bargain fee reported to be £1.25million from Schalke in January, has seen an abundance of competition arrive in the close-season.
Paulinho, Erik Lamela, Christian Eriksen, Nacer Chadli and Etienne Capoue have all been brought in, meaning that Holtby has featured in Tottenham's matchday Premier League squad on just one occasion this season.
He has not played a minute in the league but did start, and score, in Tottenham's 3-0 UEFA Europa League second leg play-off win against Dinamo Tbilisi.
Holtby has kept in scoring form, too, netting in successive Under-21 Premier League matches against West Ham and Norwich City, and said he was happy to be named in the club's 25-man squad for the league season.
"I am very pleased to be in this squad," he told The Express.
"You need a big squad if you want to challenge for trophies and be strong in every competition."
Holtby made 17 appearances for Tottenham last season following his mid-season arrival, but failed to score.
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