"It's good just to get my feet wet," he said.
And in a season already lost in terms of the standings, this was as good a time as any to continue that initiation process.
Barthmaier plans to enter Spring Training next season vying for a rotation that is wide open. The 24-year-old can only hope that his three games in a Major League uniform will make him at least a bit more prepared.
His first two starts in the Majors weren't pretty -- 5 1/3 innings pitched, 12 hits, nine runs. So considering how his first taste of the big leagues went, Saturday might not have been a big step forward, but neither was it a step back.
Barthmaier almost matched that cumulative innings total, as he finished five frames Saturday.
He recorded the first two outs -- though San Diego's Will Venable just missed a leadoff home run -- before running into trouble. A walk to former Pirates outfielder Brian Giles extended the inning for first baseman Adrian Gonzalez to double home the game's first run.
Barthmaier then left his first pitch to third baseman Kevin Kouzmanoff belt-high. Kouzmanoff turned on it and sent it over the outfield wall to give the Padres an early 3-0 lead.
"He hung two breaking balls and that cost him three runs," manager John Russell said.
But what looked to be a repeat of those first two outings did not come about. Barthmaier allowed two hits in the second, but finagled his way out of any more trouble in the inning. He then settled down and allowed only two baserunners in his final three innings.
Russell attributed the in-game improvement to simple relaxation.
"He just settled down," Russell said. "He was trying to guide the ball a little bit earlier. He seemed like he was pushing it out of his hands instead of the life it had after that."
In doing so, Barthmaier looked more like the pitcher who posted a 3.53 ERA in 16 Triple-A starts than the right-hander who appeared overmatched in his first two starts in the Majors.
Barthmaier's analysis differed slightly from his manager's, as the righty conceded his initial struggles more to an early lack of rhythm than being tense.
"I was relaxed the whole time," said Barthmaier, now 0-2. "I just felt like I was pitching to their strengths at the beginning of the game. I just got a little tight in the first from sitting on the bench and left some pitches up. I figured some stuff out after that."
Despite the turnaround from Barthmaier, those three first-inning runs would be enough for San Diego to even the series at a game apiece. Padres starter Chris Young entered the game 3-0 and with a 1.52 ERA in four career starts vs. the Pirates and would end the night with another win.
Adam LaRoche drove in the Pirates' only run off Young with a two-out double in the third. LaRoche's 83rd RBI of the season scored second baseman Freddy Sanchez, who finished with two hits. Sanchez has now hit safely in his past seven games.
Young, however, responded by setting down the next 10 Pirates he faced.
The Pittsburgh bullpen did its job -- combining for three scoreless innings -- but the offense did not, going 0-for-8 with runners in scoring position.
The Pirates' most opportune chance to carve into that deficit came and went in the seventh against Padres reliever Mike Adams. Andy LaRoche followed Steve Pearce's leadoff single with a walk, and both moved into scoring position on a sacrifice bunt. But strikeouts by pinch-hitter Jack Wilson and Nate McLouth ended the threat.
Pittsburgh's only other run came the following inning, when Jason Michaels' two-out RBI triple in the eighth scored Ryan Doumit. Michaels would be stranded at third, however, when Steve Pearce lined out to first to end the inning.
Trevor Hoffman then shut the door on any potential comeback bid with a perfect ninth to pick up his 30th save of the season. Hoffman has now saved 30 games in 13 seasons, a Major League record that he continues to extend.