The game was locked at 2-2 heading into the final inning against defending league champion Princeton, and it looked as if Penn might take down its top rival.
The Quakers had just tied it up in the bottom of the sixth on a home run by junior Stephanie Reichert, and Princeton had not scored since the first.
But Penn's pitcher, junior Olivia Mauro, who had been cruising through the middle innings, could not finish the job.
Mauro allowed a leadoff double, and then three batters later the Tigers' Erin Snyder homered to knock Mauro and the Quakers out of the game.
Princeton handed Penn a 5-2 defeat in the second game of the doubleheader on Saturday to complete a sweep. Penn had fallen 4-0 in the first game.
Penn came into the weekend on a hot streak, having won four of its last five games, but the Quakers could not keep pace with the top team in the Ivy League.
"I was a little bit tired," Mauro said. "I pitched a lot of innings coming off sickness, but they're good hitters. I tested them and they beat me."
Mauro (3-2) gave up seven hits and five runs -- three earned -- over 6 1/3 innings, and took the loss for Penn (11-16, 0-2 Ivy).
After the Tigers (16-8, 2-0) scored two unearned runs in the first, Mauro was in complete command for the next five innings, allowing only two hits.
The Quakers climbed back into the game with leadoff home runs in two consecutive innings.
Junior Julia Cheney started the bottom of the fifth with her second home run of the year.
In the sixth, junior Stephanie Reichert followed Cheney's example with a solo shot to tie the game at two.
Penn then threatened to take the lead, putting runners on first and second with one out. But Erin Snyder came in to pitch for Princeton in relief, even after pitching a complete game in the opener, and struck out the first two batters she faced to get out of the jam.
Game 1 was a pitcher's duel early on, with neither team scoring until the sixth.
Penn freshman Emily Denstedt (7-8) scattered seven hits through the first five innings yet was able to keep the Tigers off the board.
But she couldn't escape a leadoff double in the sixth. After striking out the next batter, she allowed a home run to Jackie Araneo.
Princeton added two more in the inning for a total of four runs on five hits.
That was more than enough of a cushion for Snyder.
Denstedt's counterpart was brilliant, mowing down Penn's lineup en route to a three-hit shutout. Snyder had 14 strikeouts on the day and struck out the side on three separate occasions.
Sophomore Christina Khosravi was the lone bright spot for Penn's offense in the opener, going 2-for-3 with a double.
If this weekend showed anything, it's that the Quakers continue to overcome one of their biggest obstacles this season: having only three pitchers. Penn pitchers allowed only 3.5 earned runs per game in the doubleheader.
"We were a little worried at the beginning with only three pitchers," Mauro said. "But we're doing a good job now, so I'm really proud."
Although they dropped both games, the Quakers say they are happy that they were able to hang with the Tigers, who have won the Ivy League title three out of the last four years.
"To hold Princeton like we did in that first game until the sixth inning and to play as well as we did today, we just have such a positive outlook for the rest of the season," Cheney said.
Penn travels next to Temple on Tuesday before continuing the Ivy League season with home games against Brown and Yale next weekend.
