After dropping two points in the draw at Newcastle on Sunday, Spurs are now three behind fourth-placed West Ham.
Manager Jose Mourinho criticised his players in the wake of the game, and now Son has urged the Tottenham squad to stand up and fight across the final games of the season.
As well as pushing for the Champions League places, Spurs will face Manchester City in the Carabao Cup Final at Wembley on April 25 as they look to win a trophy for the first time since 2008.
“We’ve nine games left with the cup final and we have to be ready, we have to be warriors," Son told the club website. "That’s very important for the rest of the season.
“We’re three points off the top four, it’s tight and we all want to play in the Champions League next season, that’s our aim, that’s the club’s aim, the fans’ aim as well. That’s what we all want.
“We’re all focussed on that and we will try as hard as possible to get there.”
Spurs host Manchester United on Sunday before travelling to top-four rivals Everton a week on Friday.