Tkachuk, who didn't participate in the morning skate, was injured during practice Tuesday when he collided with defenseman Travis Hamonic.
Flames coach Bill Peters said the injury isn't serious.
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"He tweaked it a little 3-on-3 down low in our skate [Tuesday]," Peters said. "He could play easily today, but we're not going to force the issue this time of the year. If this was [opening night] against Vancouver in Vancouver, he'd be in the lineup."
James Neal, who was originally supposed to be scratched, played instead of Tkachuk. Neal started on a line with Derek Ryan and Austin Czarnik, but Peters said he could get some shifts on the top line with Sean Monahan and Johnny Gaudreau.
Elias Lindholm started with Gaudreau and Monahan.
"[Neal] might get some shifts there, but if he does it's coming off bump-up scenarios off power play, penalty kill," Peters said. "He's going to play on that line when we're at home against Vancouver (on Saturday). That plan hasn't changed. Guys are going to get moving around as we get going in the preseason."
Forwards Morgan Klimchuk, Curtis Lazar and Anthony Peluso, along with defensemen Rasmus Andersson and Dalton Prout, will play after being scratched for the Flames' 4-3 shootout loss against the Bruins in Shenzhen on Saturday.
In addition to Tkachuk, forwards Mikael Backlund and Michael Frolik, and defensemen Michael Stone and Brett Kulak won't play for Calgary.
Mike Smith will start in goal after sitting out Saturday. Jon Gillies will be the backup.
Bruins coach Bruce Cassidy said defenseman Charlie McAvoy did't play Wednesday because he's not feeling well.
"It's exciting to get back in a game and start feeling it a little bit," Smith said. "Not too much pressure on me; just want to go out there, get a good feel and try to push camp along."
The Flames and Bruins will return home following the game to join the players who are already participating in the North American portion of their training camps.
"Hopefully come December we're in a good spot and we can look back and say we made the most of this trip and it helped us get off to a good start," Gaudreau said.
