Gian Piero Gasperini urged his Atalanta side to keep their cool ahead of the biggest game in the club's history as they face Valencia in the Champions League last 16, first leg on Wednesday.

"The team must have clear heads," the 62-year-old said during his eve of match press conference at the San Siro.

"We have already played many important games, we will have to draw on our experience of those games here."

The Spanish club have been depleted for various reasons and are missing six players including injured Ezequiel Garay and suspended fellow central defender Gabriel Paulista, with midfielder Alessandro Florenzi down with chicken pox.

"It doesn't make me think it will be easier," said Gasperini.

"When a team plays in the Champions League they have an extensive squad and those who play give the maximum.

"Valencia represent an elite of Spanish football. They came first in a very difficult group winning against Ajax and Chelsea."

The match in Atalanta's first campaign in the top-tier of European football will be played at the 80,000-seater San Siro, home to Inter Milan and AC Milan, as Gasperini's side's own Gewiss Stadium 55km away does not meet UEFA requirements.

"This is our first great success, moving so many people, we have never played with such a big crowd," added Gasperini.

"But we mustn't get carried away by the euphoria of it."

The visitors' coach Albert Celades warned despite their injury woes his outfit were ready to defuse the free-scoring Italians, who are fourth in Serie A but lead the way with 63 goals in 24 games.

"Atalanta are a goal bomb. We will try to use our available weapons to defuse them," said Celades.

"We are facing a really attacking team, that has scored the most goals in Serie A. Their season is impressive, they are an uninhibited team that goes on the pitch to have fun.

"They love to go forward. Despite our absentees we will try to get by with the players we do have available."