Madrid-born Morata was an Atletico fan as a boy but came through the youth ranks at neighbours Real, before joining Chelsea for €62 million last summer. He has scored six times in his first six Premier League appearances, including a hat-trick in last weekend's 4-0 win at Stoke.

Morata arrived at Stamford Bridge as a direct replacement for Costa, who has rejoined Atletico for around €55m, although he cannot feature for the La Liga outfit until January due to their FIFA imposed transfer ban.

Asked at Tuesday's news conference at Atletico's new Wanda Metropolitano ground to compare the two Spain international No. 9s, Simeone preferred to praise Wednesday's opponent.

"I'll talk about Morata," Simeone said. "I'll not talk about Costa because he's not playing for Chelsea any more. Morata is a very important player, with great movement in the box, he knows how to play with his back to goal and can keep the ball. He'll perform really well at Chelsea as the great player that he is."

Simeone's side eased past Chelsea in their last meeting in this competition, in the 2014 semifinals, when Jose Mourinho was Blues boss. The Argentine coach said things were "very different" now with Antonio Conte in charge at Stamford Bridge, while dismissing the idea that the Italian had copied some of the ideas which have made his Atletico a success in recent seasons.

"I reckon that Chelsea are very different now to the 2014 semis," he said. "They're intense, have a good balance, work hard as a team to defend and they know what their jobs are.

"They're a tough team with a top manager who instilled his mentality into the team. There is a similarity between the teams, but it is not that Conte's way of playing reflects that of Atletico. He's been playing like that for years. I've seen Conte manage Siena and Juventus and he's played in a similar way."

Asked who is the better coach, him or Conte, Simeone kept his answer to one word: "Conte!"

The game also brings former Atletico goalkeeper Thibaut Courtois back to the club where he won three trophies [Europa League, Copa del Rey and La Liga] in three seasons, before his spot was ably taken by Jan Oblak.

"Courtois and Oblak are the two best goalkeepers in the world," Simeone said. "I don't miss anything from Courtois with Oblak. They are the two best goalkeepers."

With a full squad to choose from Simeone has included ex-Chelsea veteran Fernando Torres in place of Kevin Gameiro. Croatia international Sime Vrsaljko has also not made the cut as versatile Jose Maria Gimenez perhaps comes into the team at right-back.

"I'll pick my team tomorrow based on the opponents," Simeone said. "I'm not thinking about individual players, but the side's balance. Someone in form might not start, for the good of the team.

"Dead balls might be important tomorrow. Gimenez is important for us, he can play in a number of positions. When he's at full-back it is almost like we have three centre-backs on the pitch, and we have more strength in the air."