Navarro hasn't seen Major League action since August 2011, when he was with the Dodgers.
He has spent the entire 2012 season at Louisville, where he was hitting .330 with four home runs and 27 RBIs in 57 games, but he is finally getting his call to duty in the most pivotal series for the Reds this season.
"As a player, these are the types of games you want to play in, especially being in the Minors the whole year," Navarro said. "Now you're coming up to the big leagues, and I think you're trying to prove a point. You're trying to show that you're still capable of playing at this level. I'm really excited and really looking forward to this opportunity."
Navarro, an eight-year veteran, has had stints with the Yankees, Dodgers, Rays and now the Reds.
He was an All-Star selection in 2008 on a Rays team that made a run to the World Series.
"This guy has been in the big leagues before," said Reds manager Dusty Baker. "It's not like it's his first game like a rookie. This guy is a former All-Star, and he was in the playoffs with Tampa Bay. This guy is more than ready. He was with us in Spring Training, and he was doing well in Triple-A."
The coaches told Navarro he would be starting Saturday three days ago when he arrived in Cincinnati, and the 28-year-old catcher said he didn't expect any lull between himself and the pitching.
"It's still the same," Navarro said. "I caught with almost all these guys in Spring Training, and I got the opportunity to go to the video room and watch some videos of what they do and what they don't like to do."
If Navarro continues to fill in for Mesoraco, he'll be in the starting lineup again Sunday, when Homer Bailey takes the mound.
"I'm just looking forward to today, and we'll think about tomorrow when it gets here," Navarro said.