By Bruce Levine–

(CBS) With baseball’s free-agent closer’s market pretty well dried up now that Aroldis Chapman (Yankees) and Kenley Jansen (Dodgers) have signed five-year deals, willing trade partners should emerge for the White Sox, who have close David Robertson on the trade market.

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Both the Nationals and Marlins are in need of a lockdown closer. Washington already tried to acquire Robertson last week, when it acquired Chicago outfielder Adam Eaton in exchange for three pitching prospects.

The 31-year-old Robertson is a shorter-term buy for teams, as he has two years and $25 million left on his original four-year deal. For the rebuilding White Sox, prospects are the name of the game, and the Nationals still have a robust system despite their recent trade of highly touted youngsters.

Having acquired five pitching prospects recently in trades with the Red Sox and Nationals, the White Sox can now turn their focus to obtaining position players for the future. Victor Robles, a 19-year-old outfielder, is Washington’s highest-rated prospect and would be a good place to start in potential negotiations.

A native of the Dominican Republic, Robles was originally signed in 2013 for $225,000. Across three lower-level minor league stops in 2016, he hit .280 with nine homers, 42 RBIs, 37 stolen bases and a .798 OPS in 110 games. He finished the season at high Class-A.

Robles is a projected center fielder or right fielder, with a 65 grade arm. (The top grade is an 80, and a 60-plus arm is considered excellent.) To his credit, Robles doesn’t strike out much, with just 77 whiffs in 504 plate appearances last season. He doesn’t walk much either, with 32 bases on balls in 2016.

The makeup and other baseball instincts of Robles all seem to check off as well, though his home run power can’t yet be projected with much certainty by the scouts who have seen him often. Baseball America projects Robles to most likely be ready to start in the big leagues by 2019.

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In any trade match with the Nationals, catching should also be a part of the equation for the White Sox. That’s a spot that’s been a black hole for the White Sox organization. Pedro Severino, a 23-year-old form the Dominican Republic, could be a potential match.

His best tools are on the defensive side. He’s consider to have a strong arm and is a plus player in receiving and pitch framing aspect of the equation. Some believe he’ll be major league ready in 2017 after he appeared in 16 games for the Nationals last season. He hit .271 with a .653 OPS in 82 games at Triple-A.

Elsewhere, the Marlins are in a competitive frame of mind and may get into the Robertson bidding. They have more quality pitching prospects than position players among their top-rated prospects.

Luis Castillo is a right-hander who’s a converted bullpen arm who could be a part of a deal with Miami. He pitched at Class-A and Double-A in 2016, with a 4.12-to-1 strikeout-to-walk ratio. He can reach the upper 90s but isn’t a huge strikeout pitcher. Still, at 24, he may not fit a White Sox rebuild.

Right-hander Tyler Kolek, 20, was the Marlins’ first-round pick in the 2014 amateur draft and may be a project worth gambling on for the White Sox, though he’s working back from Tommy John surgery, from which he’s expected back in April or May. He has a low-to-mid-90s fastball with a solid two-seam sinker, with top-of-the-rotation potential according to some scouting reports.

If a deal doesn’t match up with the White Sox, the Nationals and Marlins could turn to Rays closer Alex Colome, a 27-year-old under contract control through 2020 who was an All-Star in 2016.

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Bruce Levine covers the Cubs and White Sox for 670 The Score and CBSChicago.com. Follow him on Twitter @MLBBruceLevine.