This will be his first appearance in the series against the Tampa Bay Lightning. The 40-year-old blueliner has been a healthy scratch through the first three games. He last played May 25 in the Western Conference finals against the Anaheim Ducks.
"I'm really excited," Timonen said, admitting he still expects to feel some nerves Wednesday despite being a veteran of 1,108 NHL games.
Timonen said it has been a difficult stretch for him, watching from the sidelines.
"It's been tough. I'm not going to lie to you," Timonen said following the team's morning skate.
There was no word from the Lightning about goaltender Ben Bishop, who appeared to be dealing with some sort of groin or leg injury while making 36 saves in a gutsy performance in Monday night's 3-2 victory. Bishop left twice during the third period of Game 2 on Saturday night, and the team has not provided a reason for his twin departures.
Bishop participated in the morning skate ahead of Wednesday night's game.
"I think we're in the same holding pattern as we were 48 hours ago," Lightning coach Jon Cooper said.
Blackhawks coach Joel Quenneville commended Timonen on his professionalism while not playing.
"I'm sure deep down he's been waiting for this moment," Quenneville said.
Though defenseman Johnny Oduya exited Game 3 briefly with an undisclosed injury, he is expected to play in Game 4, as well. In addition to the defensive changes, Quenneville is subbing in Kris Versteeg in place of Bryan Bickell in Wednesday's lineup.
Information from The Associated Press was used in this report.