Saints host the reigning champions this weekend, before visiting Bournemouth on Tuesday and then welcoming Sunderland to St Mary’s the following Saturday.
Having climbed into sixth position, on the back of a six-game unbeaten run in which they have not conceded, Ronald Koeman’s side are in the thick of the fight for a place in Europe next season.
With Chelsea seven points behind them in the table and a dozen fixtures left, Saturday’s game is another opportunity to reinforce their prospects, and Ward-Prowse believes this three-match spell, in which they will hope to complete the double over each opponent, could be a vital one.
"I think we could look back on it at the end of the season and it could be a defining period for us,” said the midfielder, who was speaking at Redbridge Community School, where he was promoting the Saints Foundation
’s Saints Connect project, which is being backed by BT Sport and the Premier League.
“We've got to make sure that we're professional, we recover right and make sure that we're ready to go again.
“I know all the lads and the management staff, we're all wanting to get the club back into Europe and I think these three games could be pivotal towards that.”