Inter Milan boss Leonardo believes Sunday's trip to Udinese will be the sternest test of his reign at the European champions.

With five wins from five since taking over from the sacked Rafael Benitez on Christmas Eve, Leonardo's influence is turning around the club's fortunes after a dismal start to the season.

But Udinese are in a rich vein of form at the moment, with a 4-4 draw at the San Siro against Serie A leaders AC Milan followed by a 4-2 win over Genoa in their last two league games, leaving them in eighth place, just five points behind fourth-placed Inter.

Leonardo sounded a note of caution to his players ahead of the clash and insisted it was far too early to be thinking of Serie A glory.

"We will be facing players in great shape, who are getting excellent results and we must be very careful," Leonardo said.

"Alexis Sanchez and Antonio Di Natale form a very interesting partnership that is extremely difficult to defend against."

"I think tomorrow might be truly the toughest test we've had yet. In any case, we too are in a positive period of form and I trust my team to read the situation with their tactical intelligence."

"As for the Scudetto race, I don't think anything is decisive right now. There's a long way to go. The important thing was to close the gap from the top and we have done that."

Winger Philippe Coutinho is back in the Inter side after a prolonged absence with a thigh strain, as is Thiago Motta, but Walter Samuel, Diego Milito, Wesley Sneijder and Julio Cesar are unavailable.