By TYLER KEPNER

Published: June 18, 2004

PHOENIX, June 17 - In some ways, Mike Mussina's groin injury could not have come at a better time for the Yankees. The team is playing very well, the trading deadline is approaching, and the injury gives the Yankees a chance to show off Brad Halsey, a fast-rising prospect.

When Halsey, a 23-year-old left-hander, starts on Saturday at Dodger Stadium, other teams will notice. The Seattle Mariners will have a scout there, and Halsey could figure into the Yankees' attempts to get Freddy Garcia, the Mariners right-hander.

The Boston Red Sox and the St. Louis Cardinals are also interested in Garcia.

The Yankees do not expect to make a deal soon, but they scouted Garcia's last start and the Mariners have taken an active interest in scouting the Yankees' players.

They scouted José Contreras's start at Yankee Stadium last week, but Seattle would need the Yankees to pay the bulk of Contreras's remaining contract. Seattle needs a young catcher, and the Yankees' top prospect is a catcher, Dioner Navarro.

The Mariners have scouted Navarro as far back as mid-May, and have received positive reports.

Mariners scouts also liked Eric Duncan last season, when the Yankees drafted him in the first round.

Then there is Halsey, whom the Yankees compare to Brandon Claussen, the left-hander who beat the Mets last June and was traded to Cincinnati for Aaron Boone a month later.

"His demeanor is a lot like Claussen, the way he goes about his business," said Gordon Blakeley, the Yankees' senior vice president for player personnel. "He's also a lot like Claussen in that we don't want to trade him. We don't have a lot down there, pitching-wise. If he pitches great, maybe we don't need to make a trade."

Halsey was the Yankees' eighth-round draft choice in 2002, when he helped lead the University of Texas to the College World Series title.

He went 17-9 at two minor league levels last season, and is 6-2 with a 2.52 earned run average at Class AAA Columbus. He has allowed just one earned run in his last 29 innings.

"He has poise," said Mark Newman, the Yankees' senior vice president for baseball operations. "He's a strike thrower who throws his fastball to both sides of the plate and changes speeds. He's surprised people."

Halsey throws a fastball between 88 and 91 miles an hour and challenges right-handers with sliders under their hands. Blakeley said Halsey threw 26 changeups in one recent start.

"He's not a flamethrower," Newman said. "He's a pitcher."