CHICAGO (AP) _ Edgar Martinez hit a grand slam and the Seattle Mariners collected 15 hits in the nightcap Monday night to rout the Chicago White Sox 14-6 and complete a sweep of their doubleheader.

Martinez, who hit a two-run homer in Seattle's 5-2 victory in the opener, connected for his fourth career grand slam in the eighth inning, off Bill Simas. It was his 20th homer of the season for Martinez, who had seven RBIs in the doubleheader.

Seattle, which began Monday with a three-game losing streak, had been averaging under three runs and seven hits in its previous nine games, but that was before a double dose of White Sox pitching. They had 27 hits in the twinbill.

Seattle rookie Freddy Garcia won the opener for his 14th victory _ three shy of a Mariners' rookie record _ as Russ Davis hit a key two-run single.

In the nightcap, the Mariners had four-run outbursts in the first, fifth and eighth innings to complete the sweep.

Tom Lampkin drove in two first-inning runs with a bases-loaded double off Carlos Castillo, whose balk moved a runner into scoring position. In the fifth when the Mariners chased Castillo (1-2), Ken Griffey Jr., Martinez and Ryan Jackson had RBI singles.

Greg Norton hit two homers in the nightcap for the White Sox and Paul Konerko added a solo shot.

Ken Cloude (4-4), just recalled from the minors, went 5 2-3 innings, allowing seven hits and four runs.

Garcia (14-7) threw a 139-pitch, 12-strikeout shutout six days ago against Detroit. On Monday, he lasted just 5 1-3 innings.

``Freddy lost his stuff and he lost it quick,'' Mariners manager Lou Piniella said.

``Fans love shutouts but it shows a start or two afterward. The key is having the right bullpen combination.''

The Mariners, who broke a three-game losing streak, got strong performances from Jose Paniagua and Jose Mesa to close out the win.

Paniagua went 2 2-3 innings, allowing one hit, and Mesa pitched the ninth for his 30th save, striking out Frank Thomas to end the game with two runners on.

``A typical Seattle save,'' Piniella said. ``Mesa gets the job done. He made it a little exciting at times. But he threw some good fastballs past Frank Thomas.''

Garcia won his third straight start, allowing seven hits and two runs in the 5 1-3 innings. Mark Langston in 1984 and Dave Fleming in 1992 won 17 games as Mariners rookies.

Chicago lefty Jim Parque (9-11) lost his fifth straight decision, allowing nine hits and four runs in 6 2-3 innings. He walked Martinez and Jay Buhner to start the sixth and Russ Davis delivered a two-run single after a sacrifice by Dan Wilson for a 4-2 Seattle lead.

Brian Hunter added an RBI single in the eighth off reliever Sean Lowe.

``I'm not disappointed in my performance,'' Parque said. ``I feel I'm getting better and better. The walks hurt and Edgar hit a changeup when he was on his front foot.''

Martinez hit his 19th homer one out after a single by Griffey in the fourth. Mike Caruso's two-out single in the third scored Craig Wilson, who had doubled, with Chicago's first run. The White Sox tied it in the fourth on a single by Paul Konerko, double by Carlos Lee and RBI grounder by Craig Wilson.

Notes: Ray Durham had to leave the second game in the first inning after straining his left hamstring while running to first on a leadoff single. Craig Wilson replaced him. And Chicago reliever Scott Eyre had to come out in the sixth with a pain in his left shoulder. ... The Mariners have used 13 rookie pitchers this season. ... The Mariners lead the majors with 201 homers. ... It was the 17th doubleheader at new Comiskey Park which opened in 1991 and the first time the White Sox have suffered a twinbill sweep. Included in those 17 doubleheaders is the longest 18-inning twinbill in major league history, between the White Sox and Rangers in 1995, that took seven hours, 39 minutes to complete. ... Chicago used a shift on Griffey, sending shortstop Caruso to the right of second and moving third baseman Craig Wilson near the second base bag. ... The doubleheader was scheduled to make up an April 22 rainout. ... Before the second game, the Mariners announced they had sent Steve Sinclair to Triple-A Tacoma and called up Cloude. ... Norton made two more errors, giving him 25 for the season.