The Belgium goalkeeper is in his third season on loan in Madrid and the two clubs have yet to announce whether he will return to London next term or stay in the Spanish capital where he has been a key figure in Atletico's remarkable run of form.
As part of the loan deal the clubs agreed a penalty clause that meant Atletico would have to pay a hefty fee to deploy him against Chelsea but UEFA said such a stipulation was against competition rules.
"To me he seems in exactly the same state of mind as his 20 fellow squad members," Simeone said ahead of the semi-final first leg at the Calderon.
"There is a great deal of enthusiasm," added the Argentine whose side are closing on a first La Liga title since 1996 when a team featuring Simeone won a Spanish league and cup double.
"They are experiencing an important moment for the footballers, the institution and the fans. We are in a hopeful situation and we will try to give our best."
Atletico warmed up for Tuesday's game with a 2-0 win at home to Elche while Chelsea slipped to a shock 2-1 home defeat by struggling Sunderland, manager Jose Mourinho's first Premier League defeat at Stamford Bridge in 78 matches.
Simeone's side are in the last four of the Champions League for the first time in 40 years and are the last unbeaten team in the competition, having won eight and drawn two of their 10 matches.
One man who could also be forgiven for having split loyalties on Tuesday is Chelsea's Spanish striker Fernando Torres.
Born in the Madrid suburb of Fuenlabrada and a product of Atletico's academy, Torres became the club's youngest captain at the age of 19 and scored 84 goals in 214 La Liga appearances before joining Liverpool in 2007 and moving on to Chelsea three and a half years later.
"He loves this club very much and he always takes an interest in what is happening with the team," Simeone said.
"He might play (on Tuesday) and it is normal that when the referee blows the whistle the fans won't be behind him. But when the game is over and even before it he will get the ovation he deserves.
"He is one of us, a lad who is loved here. He will always be part of the Atletico family wherever he is."
- Sports & Recreation