Thomas Tuchel knows record-signing Romelu Lukaku is going through a lean patch on the pitch, but is unsure what the solution is. But the Chelsea manager promised that team would “protect” their precious asset and would try to get more out of him ahead of the first leg of their last-16 Champions League tie at home to Lille on Tuesday.

The Belgian striker once again underperformed in their team’s last Premier League game. Lukaku had seven touches against Crystal Palace in Saturday’s 1-0 win — a record for the fewest involvements in a single Premier League match by a player who has completed the full game.

The 28-year-old has scored five goals in 17 league games this season, raising questions over his hefty price tag and if he fits in Tuchel’s system at Chelsea.

“What can I do? I don’t know. Well, now we have to deal with it,” Tuchel told reporters on Monday.

“The data is out there and the data speaks a certain language, so he was not involved in our game. It sometimes (happens) like this with strikers if they struggle with self-confidence or to find the space and get involved against a good defensive team.

“It’s of course not what we want or Romelu wants. But it’s also not the time to laugh about him and make jokes about him. He is in the spotlight of course and we will protect him because he is our player.”

Azpilicueta hope

Tuchel said defender Cesar Azpilicueta will likely feature in Tuesday’s match but winger Callum Hudson-Odoi and midfielder Mason Mount are still doubtful. Azpilicueta had returned to training after suffering a groin problem, while Mount could train later on Monday as he recovers from a ligament issue. Hudson-Odoi had inflammation in his Achilles.

“Azpi looks much better than Callum. Callum did not train on Sunday, Azpi trained and has no reaction so if it stays like this he is available for tomorrow (Tuesday),” Tuchel said.

“Mason did a very good individual session, I think he will try to come back to team training but he was out a little bit too long to start. Perhaps he is involved in the squad, he has not trained with the team yet.” Chelsea won the Champions League last season after beating Manchester City in the final.

Allegri alert

Juventus coach Massimiliano Allegri will not be taking Villarreal lightly ahead of their Champions League last-16 first leg on Tuesday, saying the Spanish team are experts at getting results against Europe's big sides.

Allegri got Juve through four of five Champions League round of 16 ties during his first spell in charge, his only elimination coming against Pep Guardiola’s Bayern Munich in 2015-16.

However, Juve have fallen at the last-16 stage in the last two seasons under Maurizio Sarri and Andrea Pirlo, with Allegri issuing a warning about a team who beat Arsenal and Manchester United en route to winning the Europa League last term.

“It’s not an easy route to the quarter finals at all, we have a 50 per cent chance of progressing,” Allegri told a news conference on Monday. “They came through a very good group like us.

“They are experts against the very best teams and have got some great recent results. They have a very good coach who does not give advantages.

“Any positive result is good, with the away goal rule having changed. Before you could lose one and win one and you were through, now it’s different. A draw in Spain would be a great result.”

Morata focus

Allegri said January signing Dusan Vlahovic will make his Champions League debut at Villarreal, alongside Spanish striker Alvaro Morata.

Morata responded to media reports that he was close to moving to Barcelona in the January transfer window, especially after Vlahovic’s 70 million euro signing. “It is not important (whether he was close to Barca move),” he said. “I talked to the coach about it when the transfer market was there and we talked about the ideas he had.

“He told me how important Dusan’s arrival would be for me and so it was. If it were up to me, I would always stay here at Juventus.”

(Written with agency inputs)