Toreros' pitchers Calvin Drummond and Michael Wagner combined to limit Sam Houston (0-1) six hits and struck out 14 batters in the contest that was delayed an hour by rain.
Center fielder Louie Lechich, right fielder Kris Bryant and second baseman Bryan Haar each totaled three hits for San Diego (1-0).
"We faced a couple of good arms tonight," Pierce said. "We battled at home. I thought we were very aggressive. We played great defense. Drummond is a big-time Friday night guy. He is going to win a lot of ball games for San Diego this year."
The Bearkats took an early lead, loading the bases in the bottom of the first inning on an infield hit by center fielder Colt Atwood and a pair of bunt singles by right fielder Greg Olson and catcher John Hale. Atwood scored on a sacrifice fly to center by second baseman Jessie Plumlee.
Left fielder Lucas Hagberg tied the contest at 1-1 with an RBI double in the top of the fourth after second baseman Bryan Haar singled.
Shortstop Andrew Daniel and center fielder Louie Lechich produced a pair of singles to start the top of the fifth inning, sending Bearkat starter Caleb Smith to the bench. Reliever Michael Burchett gave up a hit to right fielder Kris Bryant to load the bases. Pinch hitter Dillon Checkal's single down the left field line scored both Daniel and Lechich to give San Diego a 3-1 lead.
Smith struck out three and allowed eight hits in four innings as the Bearkats starter, taking the loss. San Diego starter Calvin Drummond, the winning pitcher, was lifted with two outs in the bottom of the sixth inning after striking out 10 Bearkat batters.
Michael Wagner earned the save, striking out five Bearkats in the final three and a third innings.
With two outs in the bottom of the sixth, shortstop Corey Toups reached on an error by the shortstop. Atwood was hit by a pitch and Olson walked to load the bases. Toups scored on a wild pitch as Sam Houston cut the margin to 2-1.
Haar's two-out single down the left field line scored Bryant who led off the top of the seventh. Then Lechich added an RBI single in the top of the eighth to put USD up 5-2.
Kevin Miller kept the Kats alive with an RBI single with two outs in the bottom of the ninth.
The Bearkats and the Toreros will play the second game of the series Saturday at 6:30 p.m.