TEMPE, Ariz. -- Nearly four full seasons into his NFL career, Arizona Cardinals quarterback Trace McSorley is set to start his first game at quarterback.

McSorley, the Cardinals' third-string quarterback all season, will start Sunday night against the Tampa Bay Buccaneers, coach Kliff Kingsbury said Wednesday, because Arizona's backup, Colt McCoy, is still in the concussion protocol after suffering a head injury in Sunday's loss at the Denver Broncos.

McCoy started against the Broncos in place of the injured Kyler Murray, who tore an ACL in a Week 14 loss to the New England Patriots.

"He's one of those guys, I hate to use the term 'gamer,' but he's got a lot of moxie, plays with a lot of confidence," Kingsbury said of McSorley. "Teammates respond to that."

McCoy is "feeling a lot better," Kingsbury said, calling the improvement "encouraging."

McSorley, a sixth-round draft pick by the Baltimore Ravens in 2019, said it's hard not to think about the opportunity to start -- especially since the game will be on prime time, on Christmas and against Tom Brady.

"It's an exciting opportunity," McSorley said. "I always want to let myself feel that excitement and feel that a little bit just so I can enjoy the moment but at the same time just being focused and ready to go."

While McSorley said he learned in high school how to be focused on one thing at a time so the big-picture enormity of a situation or game doesn't overwhelm him, the 27-year-old will also allow himself to take in the moment of his first start and let himself feel some nerves.

"My dad always said, 'If you're not nervous, it doesn't matter to you,'" McSorley said. "So, it's a good thing to have those nerves and that feel getting ready to go into a game."

Kingsbury is eager to see how McSorley -- who has played in a career-high four games while setting career marks with 166 yards and three interceptions on 15-of-29 passing -- fares after having an entire week to prepare. Kingsbury is also curious to see how McSorley carries himself when the spotlight is on him, especially after getting playing time this season only in "adverse situations."

McSorley earned his spot on the 53-man roster because of what he showed during the preseason, Kingsbury said.

"He's mobile, can move around," Kingsbury said. "He had a couple of throws you'd like to have back, but he had a couple of scoring drives.

"I just want to see how he does with some reps. It's not easy to go in there without any reps, basically throughout the entire season, with the first-team offense, so excited to see how he can perform with some reps this week."

McSorley said he's "definitely excited" about Brady being the opposing quarterback in his first start. He remembered watching Brady beat the Philadelphia Eagles in Super Bowl XXXIX when McSorley was 9.

"He's the GOAT," McSorley said. "There's no two ways to put that. But I just got to focus on what I can control. I'm going against their defense, not against him. So, that's kind of the way I try and look at it.

"But it is cool to kind of look back and realize that starting against him the first time."

McSorley will have a personal cheering section at the game, as well.

His parents and sister were already traveling to Arizona for the holidays, so it worked out well that McSorley will be starting when they're already in town, he said.

"Definitely for the first start, it will feel good to know that that they're there," he said. "Honestly, more for them. I know if they weren't here, they would be freaking out at home."