The Germany midfielder, who moved to Spurs from Schalke last January, is jostling for a place in the side alongside recent arrivals Paulinho, Etienne Capoue, Nacer Chadli, Christian Eriksen and Erik Lamela.
Holtby's only appearance of the season so far was in Spurs' 3-0 win over Dinamo Tiblisi in the Europa League, when the 22-year-old bagged his first goal since his own move to White Hart Lane.
But with Spurs looking to secure their place in the upper reaches of the Barclays Premier League, as well as playing in Europe, Holtby appears to be relishing the task of fighting for a place in manager Andre Villas-Boas' side.
"I am very pleased to be in this squad," he said.
"You need a big squad if you want to challenge for trophies and be strong in every competition.
"To be part of a big squad, it just makes your game better."