Griezmann was a 90th-minute substitute against former team Atletico, who earned a 2-2 draw away to stuttering Barca in LaLiga on Wednesday (AEST).
A €120million signing from Atletico at the start of the season, Griezmann arrived amid much hype but the star forward has struggled at Camp Nou, where he has started on the bench against Sevilla and Athletic Bilbao in recent weeks.
Griezmann has scored eight LaLiga goals this season and 14 across all competitions for second-placed Barca, who could fall four points adrift of bitter rivals Real Madrid on Thursday.
However, Griezmann has not scored since Barca's 1-1 draw against Napoli in the first leg of their Champions League last-16 tie prior to the coronavirus pandemic in February.
Asked about Griezmann, Simeone told Movistar: "I'm without words."
Diego Costa's 11th-minute own goal had put Barca ahead before Saul Niguez's penalty restored parity for Atletico eight minutes later.
Lionel Messi converted a penalty of his own five minutes into the second half to celebrate his 700th career goal, but another Saul spot-kick – in the 62nd minute – secured a draw for Atletico.
It is the first time Atletico have scored two goals against Barca in LaLiga under Simeone, whose side are third and two points clear of Sevilla with five matches remaining.
"We are respectful of Barcelona with the quality they have," Simeone said.
"The game was played as a result of what we usually do. We started well. Their goal came in an isolated play.
"Then to generate a difficult game against a team that keep the ball well.
"We tried until the end. The work was very good, a very competitive team. I'm happy."