And that's a boost for a team which needs all the help it can get in attack.
Morata went on as a substitute in the 67th minute of Saturday's 2-2 draw at Valencia. He hadn't played since hurting a muscle in his right leg against Real Madrid on Feb. 1. The former Juventus, Real Madrid and Chelsea player leads Atletico with 10 goals scored this season.
Diego Costa hasn't played since undergoing surgery on a herniated cervical disc in November. Costa has returned to training with the team, and Simeone has said that the Brazilian player should be ready for Liverpool's visit on Tuesday in the first leg of their round-of-16 game.
Liverpool will be returning for the first time to the Wanda Metropolitano Stadium where Jürgen Klopp's side won the European Cup in June.
Atlético's two goals at Valencia came from midfielders. Marcos Llorente scored from close range before Thomas Partey, who has become one of Simeone's best players this season, struck a great second goal. Partey charged toward a pack of back-pedaling defenders and drove in a powerful shot from the edge of the box.
Simeone has defenders José Giménez and Santiago Arias returning from injuries.
Even so, Atlético still has doubts about other important players.
It appears that João Félix will not be ready. The Portugal forward has been unable to practice because of a throat infection. He was already trying to recover from a leg injury sustained three weeks ago.
Right back Kieran Trippier won't be available and midfielder Héctor Herrera is also a doubtful starter.
One of Atlético's top priorities will be marking Liverpool star Mohamed Salah.
That could fall to midfielder Saúl Ñíguez, who Simeone often recruits to play at left back when he wants a tougher defender than the more attack-minded Renan Lodi.
"We have to go out there to compete, to have a good showing, and I am sure that if we do just that we will have possibilities of advancing," Ñíguez said on Sunday.
The game against Liverpool has taken on extra importance for Atlético after its difficult start to 2020. Since the start of the year it has lost the Spanish Super Cup final, been eliminated from the Copa del Rey by a third-tier team, and fallen out of contention in the Spanish league.