"Sack Pochettino now", "Not a serious club" - Chelsea fans react furiously on social media as they lose to Middlesbrough in 1st leg of EFL Cup S/F

Chelsea fans have launched a scathing attack on their team and Mauricio Pochettino following their shock 1-0 defeat to EFL Championship outfit Middlesbrough on Tuesday (January 9).

The Blues headed into tonight's Carabao Cup semi-final first-leg game at the Riverside as heavy favorites. Michael Carrick's Boro were dealing with an injury crisis and several of their first-team regulars were out of action.

The hosts felt they deserved a penalty just a minute into the game after a strong challenge from Axel Disasi on Ivorian forward Emmanuel Latte Lath. But, VAR isn't in use in the Carabao Cup, perhaps letting the Blues off.

Carrick was forced to take Lath off following that tackle, with youngster Josh Coburn coming on in his place. It was a massive blow to an already depleted Boro side.

Chelsea should have taken the lead in the 32nd minute when Cole Palmer spurned a golden opportunity. A poor pass from veteran English midfielder Josh Howson allowed the former Manchester City attacker to race through on goal.

However, Palmer curled his shot wide of the post after getting to the edge of the box. The in-form England international should have done better and he knew it.

Palmer's mistake came back to haunt Pochettino's side as they fell behind four minutes later. It was a superb counter attack from Carrick's men that was cooly finished off by English midfielder Hayden Hackney.

Chelsea were extremely wasteful and Palmer was the main culprit. He should have equalized in the 45+4th minute when Boro goalkeeper Tom Glover spilled Enzo Fernandez's shot.

The goal was gaping but Palmer could only send his shot high over the bar from close range. He fell to the floor in despair, knowing he should have got his side back into the game.

Boro's speedy English winger Isiah Jones was a real threat throughout and caused Levi Colwill problems on the right flank. He sent several dangerous crosses into the Blues' box that his teammates couldn't convert.

Carrick's side nearly found a second in the 67th minute when Daniel Barlaser blazed over the bar from just outside the box. Jones somewhat got in the English-Turkish midfielder's way.

Boro stood firm and defended right to the death to keep Chelsea at bay. It was a case of the same old story for Pochettino whose side squandered 18 opportunities throughout.

A calamitous defeat for the west London giants means they'll have to try and turn things around at Stamford Bridge next week. But, their fans were less than impressed with tonight's performance.

One fan even wants Pochettino dismissed:

"Sack Pochettino now."

Another fan gave an equally grim verdict of the Blues as a whole:

"We are not a serious club."

Here's how fans on X (formerly Twitter) reacted to Chelsea's shock defeat at the Riverside:

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Stewart Downing was shocked by Pochettino's decision to bring Noni Madueke off in Chelsea's loss

Noni Madueke didn't last the full 90 minutes.

Noni Madueke has forged his way back into Pochettino's plans as of late. The English winger was on the fringes of the first team at the start of the season but has started his side's last two games across competitions.

The 21-year-old started tonight's game and was a constant threat down the right channel. He had three shots, completed three of five dribble attempts, and won six of 11 ground duels. It was somewhat surprising when Pochettino decided to bring him off for Mykhailo Mudryk in the 63rd minute.

Former Boro winger Stewart Downing was stunned by that decision. He told BBC Sport:

"I cannot get my head round that, Noni Madueke has been Chelsea's most threatening player. I thought it would be Raheem Sterling coming off."

Madueke came off the bench to score the winning penalty in a 2-1 win against Crystal Palace on December 27. His future was somewhat uncertain at the back end of last year but he's since shown his worth.