"I think we have to be smart about it," he said. "I think that if I'm not going to be ready then it's not very smart to put me out there."
The 45-year-old right wing signed a one-year, $1 million contract with Calgary on Wednesday.
He didn't give himself a strong opening review in his first skate.
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"Not very good," Jagr said. "It was a fast pace. It's not going to be easy, these first few practices. It's a challenge.
"To be honest, it was a crazy day the last few days. I didn't know if I was ever going to play in the NHL again, and I didn't practice with any team. To put it in perspective, I was practicing and didn't see any future. It was kind of tough, especially at my age. It's not easy for anyone to practice on their own, but not to see much future … and if I was in Europe I would probably take a month to get ready before I played some games. Right now I cannot do it. But it's kind of different.
"It's a challenge. That's why I go day by day. Hopefully tomorrow I feel better. Hopefully it's going to come back quick."
Jagr did not play when the Flames opened their season with a 3-0 loss to the Edmonton Oilers at Rogers Place on Wednesday. He could, however, play in Calgary's home opener against the Winnipeg Jets at Scotiabank Saddledome on Saturday (10 p.m. ET; SN, CITY, NHL.TV).
It will be Jagr's decision, according to Calgary coach Glen Gulutzan.
"I talked to [Jagr] and he said that he's not feeling great," said Gulutzan, who coached Jagr in 2013 with the Dallas Stars. "He flew in from [the Czech Republic]. I thought he looked good.
"We'll see where he's at. That's going to be up to him because he knows. I think he's got enough games in the League to figure out when he's going to be completely ready. We talked about that. I said, 'you've got to let me know how you're feeling.' We'll see how tomorrow goes. Best part is we get another practice."
Jagr is third all-time with 765 NHL goals behind Wayne Gretzky (894) and Gordie Howe (801), and is second all-time in points with 1,914 behind Gretzky (2,857).
He also trails Howe (1,767) by 56 games played for most on the League's all-time list.
"He's going to have to get up to speed a little bit," Gulutzan said. "Things have changed from five or six years ago, certainly, when I had him before. There will be a little learning curve, but we're talking about a player whose seen a lot, seen it all. I don't think there's a drill or a system that's going to be new to him.
"He'll get that really quick."
