SAN DIEGO -- A Mariners farm system that has been stockpiling talented young starters will add another next spring as 2017 second-round Draft choice Sam Carlson is ready to return from Tommy John surgery, general manager Jerry Dipoto said Wednesday at the Winter Meetings. Carlson has pitched just three innings

SAN DIEGO -- A Mariners farm system that has been stockpiling talented young starters will add another next spring as 2017 second-round Draft choice Sam Carlson is ready to return from Tommy John surgery, general manager Jerry Dipoto said Wednesday at the Winter Meetings.

Carlson has pitched just three innings of pro ball since being selected as a Minnesota high school standout with the 55th overall pick 2 1/2 years ago, but he is back to full health and likely will start next season at Class A West Virginia.

The 6-foot-4 right-hander was ranked as the Mariners' No. 3 prospect by MLB Pipeline in 2018 after pitching just briefly in the Arizona Rookie League due to a sore elbow the prior year, but he wound up needing elbow surgery in July 2018 and hasn't thrown in a game since.

"He's in his throwing program now and feels great," Dipoto said. "He was in Seattle [at a Mariners leadership conference last week] and was extremely positive. He works his tail off. I hope so much we get to see what he's capable of."

Carlson was close to returning toward the end of last season and was throwing 94 mph while rehabbing at the Mariners' complex in Peoria, Ariz., but the Mariners decided to play it safe and not push him into game action until spring.

The Mariners made a bold move in 2017 when they drafted Carlson, because many expected he'd opt for college. Seattle managed to sign him for a $2 million bonus that was well above the $1.2 million slot allowance for his Draft position, but he has yet to see that potential play out on the field.

"He's been through a lot in young life," Dipoto said. "He's pitched three innings and done nothing but rehab in the time since. That's tough on the mind. We didn't think it was appropriate after all that to throw him out there in the dog days, so let's just be smart and let him ramp up through the offseason and take a full Spring Training rather than go out there and try to show us he's worth $2 million in five innings in September against kids in the [Arizona] league."

Despite his injury, Carlson is still ranked as Seattle's No. 12 prospect, and he now has a chance to join a group of promising young starters selected in the past two Drafts -- Logan Gilbert, George Kirby, Isaiah Campbell and Brandon Williamson -- as well as Justus Sheffield and Justin Dunn, who were acquired by trade last year.

Dipoto still quiet for now

Dipoto said he had a couple of meetings with agents on the third day of the Winter Meetings, but he doesn't believe the club is too close to signing either a starting candidate or reliever, the two primary goals still on the to-do list.

"We're just trying to keep our finger on the pulse of their markets and see where it goes," he said. "I don't expect any of that until after the holidays. And we had a really short couple of meetings with other clubs, possible trade matches that I don't think are moving along at a quick clip."

Mariners hope to be active in Rule 5 Draft

Seattle has the sixth selection in Thursday morning's Rule 5 Draft, and the Mariners will likely select a reliever if the right player is available. Dipoto said there are two pitchers they're intrigued by, but will pass if both are off the board.

"The Rule 5 Draft is always a bit of a crapshoot, but there's talent," he said.

Last year, the Mariners plucked right-hander Brandon Brennan from the Brewers and he wound up one of the few Rule 5 success stories in 2019, sticking with the team all year while posting a 4.46 ERA in 44 outings.

Netting to be expanded at T-Mobile Park

MLB Commissioner Rob Manfred announced Wednesday that all 30 teams would be extending netting beyond the dugouts in their home parks this coming season to improve fan safety. The Mariners extended their netting to the edge of the dugouts in 2018 and are now looking into how best and how far they can lengthen that for the upcoming season.

Due to the ballpark configuration, with an elbow midway between the dugouts and foul poles where the seats jut out, it's not as simple as just extending netting straight down the line to the foul poles. The Mariners have been studying the options but have not determined how far they'll extend their new netting.

The Mariners previously extended netting in 2016 to 70 feet beyond home plate and then in '18 to the outside of both dugouts to meet MLB's recommended minimums at those times, with upgraded, lighter weight mesh used in both instances to minimize the impact on fans' viewing.

Greg Johns has covered the Mariners since 1997, and for MLB.com since 2011. Follow him on Twitter @GregJohnsMLB.