The Mariners sent pitchers Sean Green and J.J Putz, and center fielder Jeremy Reed back to the Mets.
Having just turned 35 on February 2, Vargas hasn't seen many suitors come around this winter despite coming off the best season of his career. Vargas, 35, made his first All-Star team last season after posting a 2.62 ERA over 17 first-half starts, but he faded badly in the second half with a 6.38 ERA over his final 15 outings.
This will be his second stint with the Mets, as he briefly played for the team in 2007 after being traded to NY from Miami.
That kind of style is a significant change of pace for a Mets rotation that is built on hard-throwing arms with fireballers like Noah Syndergaard and Jacob deGrom.
Harvey, Steven Matz and Zack Wheeler, in particular, have spent much of the past two years on the disabled list.
Unlike other teams around Major League Baseball, the New York Mets continue to be active in free agency with spring training getting going. Robert Gsellman, Seth Lugo and Rafael Montero also provide insurance.
The move also means five of New York's top six starters have undergone Tommy John surgery at some point in their professional careers. Discounting those seasons, Vargas has averaged 188 innings per year since 2010. He did not pitch in the playoffs that year, but went 1-0 with a 3.52 ERA over three postseason starts for Kansas City in 2014.
The Royals did not extend a qualifying offer to Vargas after the 2017 season so they will not receive any compensation for Vargas signing with the Mets. He surpassed 192 innings each year from 2010-12 and threw 187 in 2014. He missed the 2008 season because of a torn labrum in his hip.
Vargas rounded out his 2017 campaign with a 4.16 ERA, 1.330 WHIP, and a whopping 18 wins. His contract also includes a club option for 2020.
In his first 16 starts, Vargas had a 12-3 record with a 2.22 ERA and opponents hit just.237 against him.