PEORIA, Ariz. -- Dustin Ackley isn't known as a power hitter, but the Mariners' top position prospect uncorked a prodigious home run in the fifth inning of a "B" game against San Diego on Monday on a Padres practice field.

The young second baseman went 2-for-4 in the Mariners' 4-1 win, a seven-inning game designed mostly to get some extra innings for pitchers on both sides.

Ackley drove a fastball over the right-field fence on a full count from left-hander Rob Musgrave, with Chris Gimenez following with another home run on the next at-bat. It was Ackley's blast that had people talking though.

"That's the best one I've hit in a while, I'd have to say," Ackley said. "Best one I've hit this year. It felt pretty good, especially against lefties, who are pretty tough. Just the battle and getting a pitch to hit, then seeing it go off the bat like that is definitely a confidence builder and good for me, as far as continuing through the rest of Spring Training."

Ackley has been hitting well of late. While the "B" game results don't count in official statistics, he's hitting .350 with two doubles and a triple in 20 at-bats in Cactus League action after coming off the bench Monday with an eighth-inning single against the Cubs.

Ackley also has seven walks in 26 plate appearances and a .519 on-base percentage.

"I feel good as far as timing and everything," he said. "Just finding some good pitches to hit and hopefully being a little more aggressive."

Ackley also started a nice 4-6-3 double play in the eighth to help Garrett Olson get out of a jam. But it's his offense that is hard to ignore.

"He's a good hitter. Not too many people can go down and scoop that ball out of there and line the ball the way he did [against the Cubs]," manager Eric Wedge said. "He swung the bat well in the 'B' game as well this morning. He's been swinging the bat well all camp."

Robertson to have surgery on left elbow

PEORIA, Ariz. -- Veteran left-hander Nate Robertson will have arthroscopic surgery on his left elbow Wednesday and be out for at least four weeks, the Mariners announced Monday.

Robertson, 33, is a non-roster invitee who was competing for the fifth spot in the Mariners' starting rotation. He will have surgery in Los Angeles by Dr. Neal ElAttrache, the Dodgers' team orthopedist who has performed previous surgeries on Robertson's elbow.

Robertson said the elbow has bothered him in his last two outings, and tests showed bone chips that need to be cleaned out. He's had three prior surgeries on the same elbow, the last in 2009.

Robertson said the Mariners have told him they want him to stay with the organization and see if he can come back and help the club upon his return, which he estimates will be June before he's ready to compete at the Major Level.

"It's terrible timing for me trying to make the club, but I'm in good hands," Robertson said. "Everybody is on the same page about still wanting me to be here, still believing I can help, understanding it's not a career-threatening surgery. Once I get healthy, then that evaluation process starts. And hopefully it starts soon."

In three Cactus League starts, he had gone 0-1 with a 7.71 ERA in seven innings of work, with 11 hits, two walks and seven strikeouts.

With Robertson unable to even begin throwing again for about four weeks, the Mariners' fifth starter now boils down to a battle between top rookie prospect Michael Pineda and returning veterans Luke French and David Pauley, all of whom have thrown well this spring.

Robertson has a 57-77 career mark with a 5.01 ERA over 223 appearances. He was with Florida and Philadelphia last season after previously pitching seven seasons in Detroit.

Carp, Halman among five roster cuts

PEORIA, Ariz. -- The Mariners sent five more players down to their Minor League camp on Monday, including outfielder Greg Halman and first baseman Mike Carp.

Halman and Carp were both optioned to Triple-A Tacoma, as were pitchers Edward Paredes and Chaz Roe. Pitcher Chris Seddon -- a non-roster invitee -- was also assigned to Minor League camp.

Halman, 23, was a late-season callup by the Mariners last year after hitting 33 home runs with 80 RBIs for the Rainiers. He'd hit .235 this spring (4-for-17) with one home run and three RBIs.

Carp, 24, has appeared in 34 games for Seattle over the past two seasons, and had 29 home runs and 76 RBIs for Tacoma in 2010. He was batting .263 (5-for-19) with no home runs and three RBIs this spring.

Paredes, 24, split last year between Double-A West Tenn and Tacoma. He'd pitched three scoreless innings this spring with two hits allowed.

Roe, 24, was acquired from the Rockies in the December trade for Jose Lopez. He spent all of last year in the Triple-A Pacific Coast League with Colorado Springs, and will start at that level again with the Rainiers after throwing two hitless innings in two Cactus League appearances this spring.

Seddon, 27, had a 5.64 ERA in 14 relief appearances for the Mariners last season. He'd given up two runs and four hits in four innings this spring.

The Mariners now have 51 players in camp, needing to get to a final 25-man roster by March 31.

Mariners report $1.7 million profit from 2010

PEORIA, Ariz. -- Despite struggling on the field in 2010, the Mariners turned a $1.7 million profit during the fiscal year ending Oct. 31, according to the club's annual report to the Washington State Major League Baseball Stadium Public Facilities District.

The Public Facilities District owns and oversees Safeco Field on the state's behalf, and the club will present its annual report to the PFD board at its quarterly meeting on March 28.

The Mariners have made a profit every year except 2008 since Safeco Field opened in mid-1999. In 2009 they reported a $3.2 million profit.

Because of a profit-sharing provision in the team's 20-year lease with the PFD, the Mariners are required to provide an annual report of the team's financial performance. Once the club reaches $200 million in profits over the course of the lease, the team will share 10 percent of its annual profits with the PFD.

Using the special calculation agreed upon in the lease, the team will deduct $1.79 million from that figure for 2010, leaving the remaining balance at $38 million. The original $200 million is the amount of money lost by the current ownership group from the time it purchased the franchise in 1995 until Safeco Field opened in 1999.

"We keep pecking away at that cumulative net loss," said Mariners public information director Rebecca Hale. "It's been reducing at a pretty healthy pace every year, which brings us closer to that day when we are going to have profit sharing with the public."

The team's lease at Safeco Field runs through 2018.