The rookie has five homers and 13 RBIs since making his season debut on April 11.
"A guy who's swinging a bat, you're going to find a place to play him," Mattingly said.
Guerrero made his fourth start at third base.
"We're getting good production out of third base. Maybe not the best numbers in the league ..." Mattingly said.
Asked about Guerrero's play at third, Mattingly said: "It has been an eye opener for us, how he has looked on that side of the diamond."
Mattingly said Guerrero has taken balls in left field.
"There's a pretty good chance you're going to see him out there," the manager said.
Morrow (1-0), signed as a free agent in December, held the Dodgers to one run and five hits while striking out four and walking one. He had no-decisions in his first three starts.
Adrian Gonzalez, who hit a three-run shot in Saturday night's 11-8 Dodgers win for his sixth homer against the Padres this season, didn't hit a ball out of the infield in going 0 for 3 against Morrow.
The teams combined to hit 10 homers in two games and 11 in the series.
Scott Baker (0-1) lost his Dodgers debut after they selected his contract from Triple-A Oklahoma City. He signed with the club on April 5 after being released by the New York Yankees at the end of spring training.
Baker gave up three runs and four hits in seven innings.
"I thought he was good," Mattingly said. "Obviously, he gave us a chance to win. You want them to keep you in the game and give you a chance to win. He took a toll off of our bullpen."
The 5-foot-6, 159-pound Amarista drove a 3-2 pitch from Baker an estimated 398 feet into the seats in right field leading off the third, his first. It came on the 10th pitch of the at-bat.
Norris, acquired from Oakland during San Diego's December roster revamp, homered to left with one out in the seventh, his first with the Padres. Norris also had an RBI single in the fourth.
Norris threw out Jimmy Rollins trying to steal second in the first. He's thrown out eight baserunners compared to only 12 last season.
San Diego's Yangervis Solarte was thrown out trying to score from first on Matt Kemp's double to center field in the first inning. He slid head-first and appeared to injure his left wrist but he stayed in the game.