Reinhart, recalled from the Abbotsford Heat of the American Hockey League on Wednesday, will be in the lineup Thursday when the Flames continue a four-game trip against the St. Louis Blues.
Reinhart, who has 11 games of NHL experience, will slot into the lineup ahead of Sven Baertschi, who will be a healthy scratch for the third straight game.
"Max Reinhart was playing very well over in Abbotsford," Flames coach Bob Hartley said. "St. Louis [is] a big, physical team and we like what Max brought to us in training camp and exhibition games. We felt like Max was the right guy for tonight's game.
"... With the injuries that we have right now, we don't have tons of options."
Reinhart, a third-round pick (No. 64) in the 2010 NHL Draft, has three points in 11 NHL games and had nine points in 13 games for the Heat.
"I'll just play my game," Reinhart said. "I'm pretty excited to just get back in the lineup and start skating."
Paajarvi has been out since Oct. 26 and Morrow has been sidelined since being cross-checked against the Winnipeg Jets on Oct. 29.
"Both guys are good," Blues coach Ken Hitchcock said. "Both guys were getting bumped [Wednesday], full participants in the scrimmage, or the little game they had going on. Good to see. We'll get a better read on them how they feel [Thursday], but they got bumped around a little bit [Wednesday]."
"I started slow," Morrow said. "The first couple days were pretty sore. I had a tough time getting out of bed even, but over a short period of time gotten a lot better.
"I think it's about a week or so now. I'm able to do about 90 percent of the things on the ice. The last thing will probably be body contact and I don't know how far away I'm from getting into that stuff."
The Blues and Flames' probable lineups for Thursday: