Make no mistake, though, it was a big one.
Russell Branyan's 418-foot three-run home run toppled Geer and the Padres, who fell 4-3 before a crowd of 22,988 after another long ball, this one by Franklin Gutierrez off Edward Mujica in the eighth inning, provided the difference for the Mariners at Safeco Field.
As for Geer, he was left to ponder his second quality start -- six innings, three earned runs -- in as many outings, though, like his last start on June 18 against these same Mariners, it left him with a no-decision.
"It still hurts to give up home runs," said Geer, who has allowed 17 home runs in 70 2/3 innings. "It's the worst thing you can do. You never want to give up a three-run home run. They can kill you."
It did Wednesday, as Geer had trouble harnessing his two-seam fastball early in the game, which led to three hits to the first four batters in the second inning. The third of those hits, a line drive to left field, turned into an out as Scott Hairston threw out Yuniesky Betancourt who tried to score from second base.
Geer wasn't out of trouble just yet, as Branyan went down and got a two-seam fastball on a full-count pitch and drove it high and deep over the center-field wall for a 3-2 lead after Kevin Kouzmanoff hit a two-run home run earlier in the inning for San Diego.
"It looked to me as though he was close to the zone and not getting the calls," said Padres manager Bud Black. "Branyan got him with the big blow but then he settled down."
Geer would not allow another run over the next four innings and departed with the score tied after Tony Gwynn singled in a run with two outs in the fifth inning.
"It was pretty rough at the beginning," Geer said of the home run and the two walks that he issued in the first inning. "... The ball was moving more than it usually does. I threw a couple of pitches that were low that looked like strikes."
With Jake Peavy and Chris Young currently on the disabled list, Kevin Correia and Chad Gaudin are now the most experienced pitchers on an inexperienced staff, as Gaudin is the only member of the rotation who has thrown more than 500 innings at the Major League level.
Pitchers like 32-year-old rookie Walter Silva, Geer and Thursday's starter Wade LeBlanc are learning on the go. Geer impressed the Padres last September with a 2.67 ERA in five starts but this is his first extended run through the league.
Silva hadn't pitched in the Major Leagues before this season and Geer and LeBlanc had a combined 48 1/3 innings before this season.
As is the case with young pitchers, the learning curve, both good and bad, can be steep at times.
"He's capable of making pitches," Padres pitching coach Darren Balsley said of Geer. "I expected success just as they do. These guys are capable of putting together good outings. They're learning, but I expect them to make good pitches."
Seattle starter Brandon Morrow didn't always do that on Wednesday, allowing a two-run home run to Kouzmanoff in the top of the second inning, a blast that landed between the out-of-town scoreboard and the second deck in left-center field. It measured 414 feet.
Kouzmanoff's .241 batting average is the highest it's been since May 1 and he's hitting .272 in the month of June with six home runs and 20 RBIs.
"The average is climbing ever-so slightly," Black said. "I like the swings. The overall at-bats are getting better. It's encouraging."
The same could be said for Geer, who still has a 5.86 ERA but is finding a way for the most part of keeping the Padres in games, even with his proclivity for allowing home runs.
"I think Josh pitched a great game, honestly," Gwynn said. "The home run was the only mistake he made. He pitched a [great] game."