Already known to have Todd Frazier, Martin Prado, Jed Lowrie and Yangervis Solarte on their radar, the Red Sox are also scouting two Pirates (Josh Harrison and David Freese), a pair of Mets (T.J. Rivera and Asdrubal Cabrera) and the Giants’ Eduardo Nunez as they search for a third baseman, according to Michael Silverman of the Boston Herald.

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Of that five-man group, the versatile Harrison may be the most difficult to acquire – especially considering the Pirates will aim to contend next year even if they don’t make a serious playoff push this season. With a .273/.352/.424 line to go with 10 home runs and 10 stolen bases across 377 plate appearances, in which he has accumulated 2.1 fWAR, the 30-year-old is having a fine campaign. Harrison is also on a reasonable contract, one that pays him $7.5MM this year, $10MM in 2018 and carries club options for 2019 ($10.5MM) and ’20 ($11.5MM). While Harrison would be an immediate upgrade at third for the Red Sox, it’s questionable how he’d fit into the organization in the coming years. Boston’s much-ballyhooed third base prospect, Rafael Devers, is nearly major league ready, and the club has Harrison’s other positions – second base and the corner outfield – covered with Dustin Pedroia, Mookie Betts and Andrew Benintendi.

Freese, 34, would also be more than a rental, as he’s due a guaranteed $4.25MM next season and has either a $6MM club option or a $500K buyout for 2019. Currently on a $6.25MM salary, the long-competent hitter has paired a respectable .245/.376/.364 slash in 271 trips to the plate with decent work at third (two defensive runs saved, 1.7 UZR/150).

The two Mets also come with control beyond this season, though the Red Sox would have the ability to decline Cabrera’s $8.5MM club option for 2018 in favor of a $2MM buyout. Cabrera, who’s earning $8.25MM now, brings a solid offensive track record to the table and has been OK in that department this year (.250/.333/.408 with nine homers in 270 PAs). However, the switch-hitter has just one career appearance at third base, which came back in 2007, and hasn’t looked good at all in the middle infield in his age-31 campaign. Cabrera has combined for minus-14 DRS and a minus-15.2 UZR/150 at shortstop and second, his customary positions.

Rivera, who at 28 is younger than Cabrera and won’t even be arbitration eligible until after the 2019 season, has survived a low walk rate (3.9 percent) since debuting last year to post quality numbers at the plate. Through 311 PAs, including 202 this year, Rivera has batted .315/.348/.469 – a line that’s either 15 percent or 17 percent better than league average, depending on whether you prefer OPS+ or wRC+. As such, he joins Harrison in looking like someone who’d be rather tough to pry from his current employer.

Nunez, a pure rental, is earning $4.2MM and has hit a playable .297/.323/.414 over 280 trips to the plate during his platform year. More impressively, the 30-year-old has stolen 17 of 20 bases, meaning he’d provide another speed threat to a Boston team that already ranks eighth in the majors in steals. Nunez is also capable of playing second, short and left field, though he hasn’t garnered particularly positive reviews anywhere as a defender.

As Boston continues to mull its options before the July 31 non-waiver trade deadline, it’ll utilize a platoon of Brock Holt and Deven Marrero at the hot corner, tweets Pete Abraham of the Boston Globe. After the Red Sox defeated the Yankees on Sunday night, they optioned third baseman Tzu-Wei Lin to Triple-A. Lin fared nicely before his demotion, hitting .280/.379/.360 over the first 59 PAs of his career, but the 23-year-old owns a meager .638 OPS in a much larger minor league sample of 1,954 PAs.