Through Saturday, Napoli's catcher's earned-run average was 5.56 in 540 1/3 innings, compared with Mathis' 4.03 ERA in 471 innings.
"ERA is very reflective of what a catcher can do," Scioscia said. "It shows what a good job Jeff has done on the defensive side."
Mathis, who is batting .213 with five home runs and 26 runs batted in, is more athletic, especially fielding bunts and tappers in front of the plate, and has a better throwing arm than Napoli.
Scioscia believes Napoli, who is hitting .300 with 16 home runs and 44 runs batted in, has the ability to be a solid major league catcher, but Napoli has been in a bit of a defensive funk, which was the subject of a meeting between Scioscia and Napoli on Saturday.
"He's gotten away from some fundamentals of pitch selection and execution, and we addressed it," Scioscia said.
Some of Napoli's struggles are in areas that are so subtle most fans wouldn't pick up on them. Scioscia, the former Dodgers catcher, gave an example.
"You want to give the right visual in the right count to a pitcher," he said. "If you're supposed to be set up off the corner and you're on the outer third [of the plate], there's a moment when a pitcher is delivering a pitch and he'll say, 'Wait, that doesn't look right.'
"That can affect the quality of a pitch, and Mike has been a little out of sync there. There are some minor adjustments he needs to make in his setup and shifting. But he's a confident kid. He's going to figure this out."
The Angels and the University of Washington football team will be sharing Locker.
Washington junior quarterback Jake Locker, a 10th-round pick of the Angels in June, has agreed to terms with the team, university spokesman Jeff Bechthold confirmed to the Associated Press on Saturday night.
Terms of the deal were not available, but the Angels will pay for the remainder of Locker's schooling, as Locker will be forced to give up his football scholarship.
The Angels, who used a 40th-round pick on Locker after the two-sport star graduated from high school, will hold the rights to Locker, a 6-foot-3, 230-pound outfielder, for six years.
"He's a fabulous kid, a great leader, and he has great ability," Angels scouting director Eddie Bane said. "We want to keep the taste of baseball in his mouth until he makes a final decision, whether to play professional baseball or football."
No harm done
Scioscia did not think it was necessary for Felix Pie to apologize after the Baltimore Orioles outfielder punctuated his hitting for the cycle Friday night with a celebration Pie acknowledged was excessive.
"He was excited; you don't hit for the cycle every day," Scioscia said. "I didn't really give much thought to it, but if he feels he went overboard with it, fine. It's not an issue."
Torii Hunter had a hit and two walks in his final rehabilitation game for Class-A Rancho Cucamonga on Friday.
The center fielder, out for a month because of a right adductor strain, has been activated for today's game and Reggie Willits was optioned to triple-A Salt Lake.
When: 10:30 a.m. PDT.
Where: Camden Yards.
On the air: TV: Channel 13; Radio: 830, 1330.
Update: Torii Hunter, who was hitting .305 with 17 home runs and 65 runs batted in when he went on the disabled list July 10 because of a right adductor strain, will be activated and in center field today for the Angels. O'Sullivan, 21, gave up 10 earned runs and 12 hits in his last two starts. The Angels tagged Guthrie for five earned runs and nine hits in seven innings of a 5-2 win over the Orioles on July 2.
-- Mike DiGiovanna