London - Frank Lampard has challenged his young Chelsea players to "make a mark" ahead of their crucial Champions League match against Lille on Tuesday after a series of poor results took the shine off their season.
Chelsea must beat the French side at Stamford Bridge to ensure safe passage to the knockout stages, with manager Lampard expecting far sharper focus than his players showed during the 3-1 weekend defeat to Everton.
He admitted Chelsea's recent poor form - just one win in five games - was his first big challenge as Blues boss, and wants his players to embrace the pressure of this week's must-win clash.
"It is a test for us and it was always going to come," Lampard said during his pre-match press conference on Monday.
"The way we are, the nature of the Premier League, this was never going to be a plain sailing, invincible season from our point of view. Teams need this test.
"Big games like this, they are crucial for the players. You can be defined as an individual and a group by success."
Lampard, who won the Champions League with Chelsea in 2012, said he had been fortunate to have enjoyed many big nights as a player.
"So these are big opportunities now for the team, particularly the young boys when it's quite new to them, to make a mark," he said. "So I think it's good, I like the pressure of this game being knockout.
"If we're going to do anything good here, we're going to have to have lots of these nights."
Lampard said his side's poor run had not yet altered his view on January recruitment plans after the club's FIFA transfer ban had been lifted.
"I wouldn't say my mind is set on anything to be changed," said Lampard, whose side are fourth in the Premier League despite their wobble.
"But you do learn from your players in tough times, not just in terms of what they do on the pitch but how their personality is.
"That was the disappointing thing at Everton. It wasn't just that we were slightly off -- I didn't like that there were individual contact moments across the game that we lost. Because that's a personality thing as much as anything else."
Antonio Rudiger is fit for just his second appearance of the season following groin trouble, with the Germany centre-back likely to step into the Blues' defence.
Lampard believes Rudiger can make an instant impact, with the 26-year-old's return proving timely as Fikayo Tomori misses out due to a minor hip issue.
"He's a good defender, it's good to have him back and he's training really well," said Lampard, of Rudiger.
"He has got a lot of his fitness work done since the injury's healed.
"People maybe overlooked the fact that we were missing a number of big players at the start of the season. Rudi is just back, so let's see what he can add to us now."