The Argentinian led his side to a 1-0 win at Valencia on Sunday - Raul Garcia's strike shortly before half-time opening up a four-point gap over second-placed Barcelona.
Like Atleti, Chelsea are embroiled in a domestic title fight, and they produced an impressive display at Anfield on Sunday to beat Premier League leaders Liverpool 2-0.
"It is clear Chelsea has a huge team because they won despite making a lot of changes," he said.
"That means we are going to play against a powerful team, something we knew.
"So they will make a lot of problems for us next Wednesday."
The sides enter Wednesday's second leg at Stamford Bridge with the score poised at 0-0, meaning Atleti would progress to a first Champions League final in 40 years with a score draw.
