Khalil Lee of the Royals warms up before the Arizona...

Khalil Lee of the Royals warms up before the Arizona Fall League All-Star Game at Surprise Stadium on Nov. 3, 2018 in Surprise, Ariz. Credit: Getty Images/Christian Petersen

The Mets strengthened a farm-system weakness Wednesday, acquiring outfield prospect Khalil Lee from the Royals as part of a three-team trade that also involved the Red Sox.

The headliner was outfielder Andrew Benintendi going from Boston to Kansas City. He switched places with outfielder Franchy Cordero, who went from Kansas City to Boston along with two players to be named (the Red Sox also sent cash considerations to the Royals).

For the Mets, the deal involved lesser-known names. They added Lee, a speedy 22-year-old, while sending righthanded prospect Josh Winckowski and a player to be named to the Red Sox.

The Mets designated catcher Ali Sanchez for assignment to make room on the 40-man roster for Lee.

Outfield is a shallow spot in the Mets’ farm system. Of their top 30 prospects, according to MLB Pipeline, only three are outfielders — and two of those three have yet to play in a game as professionals. The other hasn’t played above rookie ball.

Lee, a lefthanded hitter and thrower, was advanced for his age pre-pandemic, spending part of 2018 and all of 2019 in Double-A. In his full season at the level, he hit .264 with a .363 OBP and .372 slugging percentage — plus 53 steals, 51 RBIs, eight homers and 21 doubles.

He mostly has played centerfield but is best suited for rightfield, where his above-average speed and arm make him a strong defender, according to MLB Pipeline, which rated Lee as the No. 8 prospect in the Royals’ system.

Winckowski, 22, was one of three pitchers who came to the Mets from the Blue Jays in the Steven Matz trade last month. He had a 2.69 ERA across two Single-A levels in 2019, the most recent minor-league season.

Oswalt dumped

The Mets designated righthander Corey Oswalt for assignment Wednesday, clearing a spot for outfielder Albert Almora Jr., whose one-year contract became official.

Over parts of three major-league seasons, Oswalt had a 6.19 ERA and 1.42 WHIP. He was out of minor-league options and was highly unlikely to make the Opening Day roster.

With free-agent utilityman Jonathan Villar, who agreed to a one-year deal this week, needing to be added to the 40-man roster, the Mets will have to clear one additional space.

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