The 45-year-old right wing decided not to play in Calgary's home opener Saturday night against the Winnipeg Jets.
After arriving Wednesday from the Czech Republic, Jagr had two practices and the pregame skate Saturday with his new team.
Coach Glen Gulutzan said that when Jagr plays the first game of his 24th NHL season is his decision.
"He said he felt a lot better the second day than he did the first and that he probably needs a couple more skates, good skates," Gulutzan said Saturday. "I thought he was very good yesterday, for a 45-year-old guy to come in with no training camp. He was arguably one of our best guys yesterday, but he needs a couple more days to get up to game speed."
Second only to Wayne Gretzky in NHL career scoring with 1,914 points, Jagr signed a one-year, $1 million contract with the Flames. If he plays 57 games, he'll pass Gordie Howe's record of 1,767.