CINCINNATI -- It's by no means the end of the road for Trevor Bauer. If anything, it's just the beginning.

But after four starts in the big leagues, Bauer knows there is some work to be done.

After his worst outing as a Major Leaguer on Tuesday, the 21-year-old righty was optioned back down to Triple-A Reno to fine-tune his mechanics.

"I'm fine with it," Bauer said. "It's about winning up here, and I wasn't giving the team a very good chance to win. I'll go down and work on being able to throw strikes."

Bauer suffered his second loss of the season Tuesday in Cincinnati, giving up four runs (three earned) off one hit in just three innings.

Bauer also walked five batters and threw two wild pitches in the outing.

"It's not a big deal. It is frustrating though," Bauer said. "I know I'm so much better than this. My stuff has been terrible when I've been here, my location has been terrible and it was never like this in the Minor Leagues."

In his four starts for the D-backs, Bauer was 1-2 with a 6.06 ERA, allowing 13 runs (11 earned) while walking 13.

It's a far stretch from the numbers Bauer was putting up in the Minors.

In 16 starts in both Double-A and Triple-A this season, Bauer was 11-1 with a 2.23 ERA, 116 strikeouts and 48 walks.

"It's a different league," said D-backs manager Kirk Gibson. "Overall the game is tougher and higher. It's the big leagues. It's just a lot and it's way quicker. Guys are smarter and they're better. You can't replace experience for anybody. And he doesn't have that much experience here. It's a way different game than he's used to."

Bauer, who zoomed through the Minor Leagues after being selected third overall in the 2011 First-Year Player Draft, isn't leaving the club without leaving his mark.

He entered Tuesday's game on the heels of his best Major League outing yet, allowing just two hits to the Dodgers in six innings.

"He's got a bunch of ability," Gibson said. "He's got great stuff, but was not consistent enough with it. He needs seasoning. It'll be good for him in the end. It's part of the process."

Bauer said he struggled with a nagging groin injury in recent starts, which may have had negative effects on his starts.

"A month ago, I was completely healthy and my groin wasn't bothering me," Bauer said. "My groin didn't bother me [Tuesday], but the accumulative effect of the mental side of things, too. If you hurt your groin, your body doesn't want to push it as much. My mechanics changed and then I finally got healthy, so I was trying to get my mechanics back to where they need to be so I can execute everything. They're just so inconsistent right now."

It may not have been the grand entrance he had hoped for, but before leaving the clubhouse, Bauer left D-backs fans with one final display of confidence.

"I know I'll be fine, and I'll pitch for a long time. I have no doubts about that," Bauer said. "I have no doubts about the fact that I can get Major League hitters out and I will get Major League hitters out for a long time. I'm just not executing right now. Everyone goes through it."

D-backs bullpen continues to be saving grace

CINCINNATI -- The past two contests in Cincinnati haven't been ideal starts for Arizona.

The D-backs came out on top Monday night in a 5-3 win, but have surrendered multiple runs early in both contests, allowing four in the first three frames Tuesday.

But the D-backs bullpen has consistently saved the day for the struggling starters of late.

In the first two games in Cincinnati, the Reds have yet to score past the third inning.

"Our bullpen has done a good job," D-backs manager Kirk Gibson said. "It's been really the story of who scores first."

Arizona's 1.91 bullpen ERA since June 22 is the best for any NL team and second in the Majors behind Seattle's 1.72 mark.

It hasn't been just one guy getting the job done either.

David Hernandez has not been scored upon in 10 of his past 11 outings, posting a 1.69 ERA. Closer J.J. Putz has converted eight consecutive save opportunities and boasts a 1.20 ERA. And southpaw Mike Zagurski has allowed just one earned run in his last eight games.

After a four-day hiatus for the All-Star Game, it seems the D-backs bullpen is stronger than ever.

"When you look at all of them, the four days off are a great thing," Gibson said. "At the same time most of those guys did pick up a ball and throw. The bullpen guys go from a lot of time off to all of a sudden back-to-back."

Gibson will need his 'pen at full strength as the team is in the heart of a 20-day stretch of consecutive games to start the second half slate.

Worth noting

• Left fielder Jason Kubel returned to the lineup Wednesday after missing the previous four games with tightness in his hamstring. In his first at-bat on Wednesday, Kubel launched a two-run home run to center field.