The Hornets have made a steady start to life in the Championship after being relegated last season and sit third in the table.
They were held to a 1-1 draw last night though by Wycombe Wanderers, who came from behind to claim their first point of the season.
Ismaila Sarr opened the scoring for Watford, but the hosts equalised through Anthony Stewart to earn a draw.
And goalkeeper Foster told Hive Live Extra “I think you can expect a bit more [than the Wycombe performance].
“We’re still a very young team and it’s a bit of a baptism of fire into this league when you come up against teams like this, but we need to grow up fast.
“It’s a very, very tough league, you can’t take anything for granted. We were third going into this game and they were near the bottom of the league without a point, but we’re the ones happier with a point than them.”
Watford have blooded plenty of youngsters this season, such as teenage forward Joao Pedro, and they have caught the eye at times.
They, along with the rest of the team, struggled at Wycombe on Tuesday night, though, and head coach Vladimir Ivic has demanded more.
“We didn’t deserve the victory,” he said.. “Our opponent had better chances. We didn’t react in most parts of the game.
“In a minimal part of the game we had positions and created chances, that’s all. I agree that we can do better. It’s not a good performance tonight. We need to analyse the game and find solutions to this.”