Chelsea's Marcos Alonso feels it will be a big blow to his side's Champions League qualification hopes if they lose to Tottenham Hotspur on Sunday.
The Blues are currently fifth in the Premier League table, five points behind Sunday's opponents Tottenham, with eight games remaining.
With Chelsea getting knocked out of the Champions League by Barcelona in the round of 16, their only hopes of qualifying for next season's competition is if they make the top four.
Chelsea have lost three of their last five league games, with defeats coming against Manchester City, Manchester United and Watford.
Alonso believes Chelsea have to win against Spurs this weekend or face a very 'difficult' fight to make the top four. The 27-year-old said via Reuters: "It's not over until it is mathematically impossible, but it would be very difficult for sure if we lost.
"It is definitely a must-win game. Here at Chelsea, we have to fight until the end for every target we can achieve, and next year we have to be in the Champions League. On Sunday, we have to get a win."
Speaking about the stats surrounding both teams heading into the game, the Spaniard feels that none of that will matter when the game begins.
He continued: "I don't think the past will have an influence. I don't like stats, I think it will be a different game and we will have to give everything and be fully focused to get the three points.
"It's a massive game. We have a very important target, which is arriving at the end of the season in the top four. Starting on Sunday, it's the first important three points for us."
Tottenham star Harry Kane is set to miss the clash through injury, but the Chelsea star is convinced Spurs will be a threat without him.
He continued: "Kane is a very important player for them, that's for sure. But I think they are a very good side physically, with some quality players, and I think it will be a very tough game even without him."