Triston Casas, 21, is ranked 37th among all prospects by MLB.com, and second among first baseman. Richard Shiro/Tribune News Service

Boston Red Sox minor league teams ended spring training camp Thursday, with Double-A players heading north to Portland. Minor league rosters are not officially set, but managers have a reasonable idea who will be on their club.

“I think we have a pretty deep team,” Sea Dogs Manager Corey Wimberly said Thursday from Fort Myers, Florida, before boarding a plane for Portland.

Among the expected Sea Dogs is first baseman Triston Casas, considered by most baseball publications as Boston’s top prospect. Casas, 21, is ranked 37th among all prospects by MLB.com, and second among first baseman.

“He’s looking good, swinging the bat well,” Wimberly said. “He’s hitting in the middle, a big part of our lineup.”

Casas, 6-foot-4, 252 pounds, is a left-handed slugger, drafted in the first round out of high school in 2018 and signed to a $2.5 million bonus. In his only full season in 2019, Casas batted .256 with an .830 OPS and 20 home runs in Class A.

The Red Sox thought enough of Casas to invite him to the alternate training site late last season and to major league spring training in February.

Another player who Wimberly will use often is center fielder Jeisson Rosario, 21, once an international prospect for the Padres ($1.85 million signing bonus). San Diego traded Rosario and third-base prospect Hudson Potts to the Red Sox last year for Mitch Moreland.

This will be Rosario’s first year in Double-A. He is a career .264 hitter in the minors, with a .376 on-base percentage.

“He’ll be at the top of the lineup,” Wimberly said.

Potts is expected in Portland, too, but may not be activated right away.

Rosario and Potts are on Boston’s 40-man roster, as is Ronaldo Hernandez, who Wimberly said will be the No. 1 catcher. Hernandez, 23, was obtained from the Rays in a deal that sent pitchers Chris Mazza and Jeffrey Springs to Tampa Bay. He has a career .293 average and a .802 OPS.

Roldani Baldwin and Jhonny Pereda will back up Hernandez, with Baldwin also getting time at third base. Shortstop Ryan Fitzgerald will be in Portland. A product of the independent leagues, Fitzgerald hit .271 for Class A Salem in 2019. Middle infielder Jeremy Rivera, who played for the Sea Dogs in 2018 and 2019, is expected back. Grant Williams, who played in low Class A in 2019, is another middle infielder.

Among the outfielders joining Rosario are two minor league free agents, Johan Mieses and Joey Meneses, and Pedro Castellanos, who hit nine home runs for Salem in 2019.

The starting rotation will be headed by right-hander Thad Ward, who has climbed the Red Sox prospect rankings (ranked No. 9 by MLB.com) since being drafted in the fifth round in 2018. Two pitching prospects obtained in trades will also be starting for the Sea Dogs – Frank German (Yankees) and Josh Winckowski (Mets).

Kutter Crawford, who started five games in Portland in 2019, looks set for the rotation. Denyi Reyes started 26 games for the Sea Dogs in 2019. He’ll be back, possibly in a swingman position. A.J. Politi, up from advanced A in 2019, also could be a swingman.

Durbin Feltman returns to the Sea Dogs bullpen.

The Sea Dogs begin their season Tuesday evening at Hadlock Field, opening a six-game homestand against New Hampshire.