The crowd delighted in Bauer's unique pregame long-toss routine, which featured him throwing nearly from foul pole to foul pole in the outfield. They cheered even more when he struck out the side in the first inning.
Unfortunately for Bauer, that was the high point of the evening.
"Trevor, he wasn't very effective," D-backs manager Kirk Gibson said.
Indeed, Bauer lasted just 3 1/3 innings while allowing seven runs, one of which was unearned after his error in the fourth inning. He walked four and struck out four.
That came on the heels of his Major League debut last Thursday in Atlanta where he allowed a pair of runs on five hits in four innings.
"Obviously the outing didn't go the way I hoped it would," Bauer said. "But I think I threw the ball very well, just adjusting to a new level. It's the same game, you execute your pitches and you'll be all right. It's just they have better eyes up here and they work counts better, so yeah, they're better hitters. It's the big leagues."
Trouble locating his secondary pitches seemed to be the biggest issue for Bauer as he fell behind in counts and was not very efficient with his pitches, throwing 80 in his 3 1/3 innings.
"Unfortunately it's been too many pitches early in the game, so it kind of gets him a little tired, a little fatigued early in the game, and his secondary stuff isn't the same," D-backs catcher Miguel Montero said. "After the second inning, all you guys can tell it wasn't the same and I had to come with the fastball and the fastball was probably too much plate and you see what happened. He's just got to learn to pitch to contact, get early contact instead of striking out everybody. That's what gets him into trouble, he's trying to trick hitters too much early in the count and then gets behind."
The Padres broke through against him in the second when Yonder Alonso blasted a two-run homer to right, the first homer allowed by Bauer.
Things unraveled further for Bauer in the fourth.
After retiring the first hitter of inning, Bauer would not get another out. He allowed back-to-back hits, made an error on a bunt attempt, walked a batter and allowed an RBI single before Chase Headley's three-run double ended Bauer's night.
"I felt like as the game went on guys started to figure him out," Headley said. "He's unorthodox to say the least, there's a lot of stuff flying at you. I think the biggest thing that got him was he lost control, he put himself in some tough positions. When you do that in the big leagues, that's going to hurt you. "
Typically an aggressive pitcher as he rose quickly through the Minors after being selected third overall in last year's Draft, Bauer did not display that Tuesday.
"There's instances throughout the game that I threw the wrong pitch," Bauer said. "I think I was kind of almost pitching defensively. I wasn't as convicted on some stuff as I should have been. I have to get back to attacking hitters instead of going out there and pitching -- I wouldn't say scared tonight -- but kind of on the defensive instead of the offensive."
Part of the solution might be following his catcher's lead a little more.
"Quite a few times," Montero said when asked how often Bauer shook him off during the game. "Part of me gets a little frustrated when a pitcher shakes me off. I don't mind when a pitcher shakes me off, but it's hard, you try to guide him. A guy like this, he probably doesn't know a whole lot of those guys and he just wants to go to his stuff, and I agree with that as long as they're good, quality pitches."
The D-backs made the game a little more interesting in the fifth when Jason Kubel hit a grand slam to pull Arizona to within 8-4.