Diaz is one of the best closers in baseball. He saved a major-league-high 57 games last season, with a 1.96 earned run average and 124 strikeouts over 73⅓ innings, and earned his first All-Star nod. Diaz, 24, will be under team control for four more seasons.
The Mets, who had one of the worst bullpens in baseball last season, could have signed one or two older relief pitchers on the free-agent market and spared their improving farm system. Elite closers, while essential for those pushing for the playoffs, are seen as luxuries on struggling teams.
If the Mets — who finished 77-85 last season — hope to take full advantage of Diaz, they will need to patch the remaining holes in their roster.
The deal with Seattle would leave several doubts, because of Cano’s suspension and age, and because relief pitchers like Diaz are often volatile from year to year.
At his best, Cano is a .300 hitter who can also produce 20-plus home runs, drive in 100 runs and get on base often — a skill needed in the Mets’ lineup. He is likely to end up at second base, with the potential to play occasionally at first and third. Cano’s arrival would probably push Jeff McNeil, the second base prospect who performed well late last season, to third base (sharing it with Todd Frazier) or into a utility role.
In Bruce and Swarzak, the Mets would be giving up two of the players over 30 they signed last winter at what was thought to be discount prices. Bruce had one of his worst seasons, suffered a hip injury and hit .217 with nine home runs, while Swarzak dealt with injuries and posted a 6.15 E.R.A. in just 29 games.
As for the prospects, the Mariners were high on Kelenic entering the June draft, but the Mets nabbed him with the sixth overall pick, eight spots before Seattle picked. Although Kelenic is just 19, several talent evaluators, including some for the Mets, are enamored of his potential. There is less consensus on Dunn, 23, the 19th overall pick in 2016, but he showed improvement last season with Class AA Binghamton and raised his stock.
Bautista, 23, is a hard-throwing relief pitcher with wayward command who was acquired by the Mets in their 2017 trade of relief pitcher Addison Reed.