Seattle ? Joel Pineiro and Mark Prior are two of the brightest young pitchers in baseball, and Friday night’s duel between two young guns at Safeco Field proved it.

The two right-handers put zeroes on the scoreboard for five innings, Pineiro with his breaking ball mixed in with fastballs, and Prior, the Chicago Cubs’ touted rookie, blowing away Mariners with his scorching fastball.

But Cubs’ All-Star Sammy Sosa has a way of making any pitcher, young or veteran, a believer in his power, and Sosa flexed that power in the sixth inning. His solo home run on the first pitch from Pineiro in the sixth soared into the upper deck, leading Chicago to a 2-0 win over the Mariners in the first regular-season game between the two clubs.

One could hardly blame Pineiro, nor call his pitch to Sosa a mistake. Pineiro tried to jam Sosa with inside pitches in the slugger’s first two at-bats, giving up an opposite-field double, then striking out him out.

To open the sixth, the astute Sosa clearly was looking for what Pineiro had been throwing him all nighta fastball inside. Sosa turned on the pitch and yanked it just inside the foul pole and into the first row of left-field bleachers.

“I was very calm at home plate, and I was able to get my pitch,” Sosa said. “It wasn’t Pineiro’s fault, it’s part of the game. He was pitching well the whole time. I have to give him credit.”

The homer, Sosa’s league-leading 21st of the season, held up enough for Prior, the Cubs’ latest savior of its downtrodden season, to shut out the Mariners on four hits in seven innings. It was all the Cubs needed before a sellout crowd of 46,083, with more than a few of those fans cheering on the Cubs.

Prior (2-1) struck out 11 with only one walk, and appeared to get stronger with every inning. The Mariners got leadoff hits in the second and fourth innings, a double for John Olerud in the second and an infield single by Bret Boone in the fourth, but could not cash in those opportunities.

Prior, who only last year was pitching for USC, befuddled the Mariners with his pitch velocity and an occasional breaking ball that painted the corner and dropped out of the strike zone where it could not be hit.

At one point, Prior struck out five in a row between the sixth and seventh innings, including all three batters he faced in the seventh.

“I felt good. The biggest thing for me was I had a better mental approach than last game,” he said. “The curveball was much better tonight, and I got some great defense behind me.

“Once we got that (first) run, I got a little bit of confidence.”

The Cubs (24-35) also had their chances to score against Pineiro early, but the Mariners’ right-hander got out of jams in the first and fifth innings, stranding two runners in each frame. Pineiro (4-3) was solid in the loss, going 7-2/3 innings (123 total pitches) with seven strikeouts and four walks.

In the top of the eighth, Pineiro gave up another home run, hanging a breaking ball to Fred McGriff on a 3-2 count with two outs. McGriff deposited the pitch into the right-field seats for a solo shot, his 10th home run of the season, and Pineiro left the game in favor of Ryan Franklin.

The Mariners (37-23) lead on Anaheim shrank to one game with the loss, as the Angels won on the first night of interleague play this season. Seattle lost for the fifth time in the past seven games, and is 0-5 in homestand openers this season. The Mariners also dropped to 15-13 at home and were shut out for third time this season, the second at Safeco Field.

“We saw good pitching on both sides, we had some chances early and a wonderful opportunity in the fourth,” Mariners Manager Lou Piniella said. “You couldn’t ask for a better situation, runners on first and third, no outs.

While the Mariners’ bats were almost silent, the team’s defense shined. Jeff Cirillo made a fine play reaching into the stands to snare a foul pop to end the seventh inning, tumbling into the seats but emerging unscathed.