Nova went 1-2 with a 4.50 ERA in 10 games, including seven starts for the Yankees last season. The right-hander went 2-0 with a 1.80 ERA in five exhibition games, including four starts.
"We didn't know what Nova was going to do," Girardi said. "Obviously, we had expectations for Nova."
García had a 12-6 record in 2010 with the Chicago White Sox.
"The innings that Freddy has logged in, the wins last year," Girardi said. "He stayed healthy all of last year."
García will be fifth in the rotation.
"Finally," a smiling García said. "Of course I'm happy. I've worked really hard this spring. We'll go from here."
Colón hasn't pitched in the majors since September 2009 and earned his spot with an impressive spring training.
"Bartolo is a guy that we think can do a lot of things in our bullpen, or if needed, a spot start," Girardi said. "Not asking him to throw 200 innings might be easier on him physically. But we just thought for this fit for right now, that's where he was best and could be most productive."
Colón was ill and not at the ballpark Saturday.
"He's excited to be here," Girardi said. "He's happy. He was the wild card in all of this. I really didn't have any expectations for Bartolo. I had no idea what to think he was going to do."
Also, left-handed reliever Pedro Feliciano will likely start the regular season on the disabled list due to left upper arm soreness. He will play catch Sunday.
"You'll probably know by Tuesday," Girardi said.
Luis Ayala and Rómulo Sánchez are among those that could take Feliciano's spot if needed.
Center fielder Curtis Granderson, out with muscle soreness on his right side, remains questionable for opening day. He hit off a tee, took part in a soft toss session, ran the bases and threw.
Granderson still feels a little tightness and knows time is running out for him to be ready for Thursday's season-opener against Detroit.
"Everything was pretty good," Granderson said. "Another step forward."
The Associated Press contributed to this report.