CHELSEA have booked their place in the Europa League semi-final after holding off a late fightback from Slavia Prague to win 4-3 (5-3 on aggregate) at Stamford Bridge.

The hosts flew out of the blocks, scoring all four of their goals in the opening half hour but manager Maurizio Sarri was unhappy with how his side appeared to switch off in the second period to gift the Czech side two identical long-range strikes within five minutes of each other.

“As usual in the last two months, we started badly in the second half,” he reflected.

“In the last 10 matches we started like this match. It’s a big problem and we need a solution.”
 
“At half-time, I said the target was to start with the same application and attention as we did in the first half. But we didn’t do it and it’s not easy to understand why.”
 
After the narrow 1-0 victory in the first leg, any niggling doubts about their progression were soon banished when Pedro put the Blues ahead on the night inside five minutes.

The goals kept flowing and with the score line 4-0 going into the interval, it appeared as though it was quickly becoming a rout for Sarri’s side.

But after the restart, it was like watching a different game and some poor defending from Chelsea has rightly led to questions about the strength of their resolve.

With the race to finish in the top four of the Premier League increasingly looking like it will go right to the wire, their inability to keep clean sheets is cause for concern.

In the last month, Chelsea have conceded six goals within the first 10 minutes of the second half. It’s hard to deny that there is a correlation starting to appear and Sarri was questioned about how he’s delivering about his team talks during the interval.

“I can try not to go into the dressing room at half time,” he joked. “If I can solve the problem like this then I will try.”

It shouldn’t go unnoticed that while his current side were conceding three goals in 90 minutes to the Czech league leaders, their city rivals Arsenal who they could yet meet in the Europa League Final, managed to keep a clean sheet in both the home and away legs against his former club Napoli, who were tipped for big things in this tournament.

The two London clubs vying for a top-four finish are level on points going into the weekend but the Gunners, who host Crystal Palace on Sunday, have a game in hand.

Meanwhile, Chelsea welcome Burnley to Stamford Bridge on Monday and can ill afford to be as defensively lax as they were on Thursday.

Compounding their concerns about hosting a strong Burnley side is Eden Hazard who was in the wars all night. The Belgian suffered a series of knocks in the first half before being substituted on 65 minutes.

If Chelsea win their semi-final against Eintracht Frankfurt, they could potentially meet their fierce rivals Arsenal in the final in Baku on May 29 should they too come through their own penultimate tie against Valencia.