Spurs must pull out all the stops to finish in top four - Stellini
Spurs are fifth in the league standings with 50 points, three behind Manchester United in fourth. They have played one game more than United and two more than sixth-placed Brighton, who are just four points behind the London club.
"We have to respect Brighton but we are Tottenham in our own stadium and so we have to go strong," Stellini told reporters on Thursday.
"Tottenham has to play for the top four every time, until mathematically it's not possible."
Spurs face a tough task against an in-form Brighton side, who are unbeaten in their last seven games in all competitions, and will be without key players Ryan Sessegnon, Yves Bissouma, Rodrigo Bentancur and Ben Davies for the encounter.
Stellini said the extensive injury list has hampered his ability to make tactical changes at Spurs, adding: "We have not enough players, we have a lot of injured players.
"With the type of players we have perhaps cannot change us tactically. We were preparing something different in the past month but now we have to be patient."
However, Stellini said Brazilian forward Richarlison, who has not played since being substituted five minutes into Spurs' 3-3 draw with Southampton last month, is "getting closer" to a return.
"He trained on the pitch but he trained alone," Stellini said. "He is going well and for the next game he could be available. We are going well with Ben Davies with the plan but we have to wait a bit for him."
Stellini also came to the defence of Harry Kane against suggestions the striker went down easily after a scuffle with Abdoulaye Doucoure in a 1-1 draw with Everton on Monday, which led to the midfielder's red card in the 58th minute.
Kane had grabbed the shirt of the Mali international, who reacted by striking the England captain in the face. Kane then collapsed to the ground in apparent agony.
In an appearance on Sky Sports, former Liverpool defender and pundit Jamie Carragher said Kane "should not be going down for that".
"I think it's strange that some ex-players say something wrong about Harry," Stellini said.
"They are ex-players and they know the difference between seeing something in slow motion and living it in real motion. Also the Everton manager said it was a clear red card. Perhaps they respect Harry but they don't respect Tottenham."