The Mets are paying a heavy price in prospects in the deal that, when completed, will send Robinson Cano and Edwin Diaz from Seattle to New York.

In Justin Dunn, the Mets will be surrendering their top pitching prospect. And outfielder Jarred Kelenic ranks among the top two or three position players in the Mets’ farm system.

Dunn, a 22-year-old righty, started 24 games last season between Single-A St. Lucie and Double-A Binghamton, and went 8-8 with a 3.59 ERA and 1.33 WHIP. The former Boston College standout, who was the Mets’ first pick in the 2016 draft, struck out 156 batters in 135 1/3 innings. It was the kind of growth the Mets had hoped to receive from Dunn after a disappointing first full season in the minor leagues in 2017.

“He still needs to be finished off a little bit, but he has got all the fastball you need and it’s got life,” former Mets special assistant J.P. Ricciardi said recently. “The slider is real good, a great changeup and a real good athlete.”

Kelenic, the sixth overall pick in last summer’s draft, wasted little time impressing talent evaluators within the organization by slashing .286/.371/.468 for Rookie-level teams at Kingsport and St. Lucie. In Kelenic, the Mets saw a potential “five-tool” player.

The expectation was the 19-year-old Kelenic would begin next season at Low-A Columbia and eventually shift from center to a corner outfield spot.

The Mets are also likely to include hard-throwing relief pitcher Gerson Bautista, who made a brief appearance in the major leagues last season, as well as Jay Bruce and Anthony Swarzak.

In the trade, the Mets managed to keep infielder Andres Gimenez, who is regarded as the organization’s top minor league player. Jimenez will likely begin next season at Binghamton.