Mauricio Pochettino warned his Chelsea team to be "careful" when they play without VAR in Tuesday's League Cup semi-final first leg against Middlesbrough.

Pochettino's side will face Championship club Middlesbrough with only the on-field officials making the calls because there is no VAR technology at the Riverside Stadium.

Chelsea took part in perhaps VAR's most controversial fixture this season when they won at Tottenham in November, a game that featured nine video interventions including five disallowed goals and two red cards shown to Spurs players.

While some might suggest playing without VAR is a positive, Pochettino is aware his youthful team have grown up with the controversial system.

Many of Chelsea's players turned professional around the time of the widespread implementation of VAR by Europe's top-flight leagues in 2018.

And Pochettino said the Blues must be cautious in the face of unfamiliar circumstances.

"There's no VAR. That is a thing we need to be careful of. Our normal attitude is to play with VAR. We need to be cautious of that," he told reporters on Monday.

"We need to be in a different way in our approach. We need to change. Now, it's just the referee that is going to decide, we need to be cautious.

"It's a different game whether you play with or without VAR. I don't say it's better or worse, but it's a different game. We need to be clever in this way."

Chelsea are firm favourites to reach their first final since they won the Club World Cup in 2021, just months after lifting the Champions League trophy during Thomas Tuchel's reign.

Middlesbrough, managed by former Manchester United midfielder Michael Carrick, are 12th in the Championship and lost 1-0 at home to Aston Villa in the FA Cup third round on Saturday.

Urging his side not to underestimate Middlesbrough, Pochettino said: "To spend all our energy is the most important thing.

"Not to go there and think 'OK, we have the second leg after to play just in case (we lose)'.

"Tuesday is the most important game and we need to come back afterwards with a victory and to finish at Stamford Bridge.

"It's going to be tough. The game against Aston Villa, they lost, but they could have won. It's a good team with great ideas. It's true they've changed their system.

"They played the season in a 4-2-3-1. We know they can use this or a different system. They have good players, a good coach. It's going to be tough."