The left-hander made his first All-Star Game during the 2017 campaign, but he struggled in the second half and finished with a 4.16 ERA, 1.33 WHIP and 134 strikeouts in 179.2 innings. It was his first full season back from Tommy John surgery after he pitched just 12 effective innings in 2016 (2.25 ERA and 0.92 WHIP).
There are certainly injury concerns with Tommy John on his resume—especially since he pitched just 43 innings in 2015—but it was his second-half drop-off in 2017 that should raise eyebrows even with this new deal.
According to ESPN.com, Vargas was one of the best pitchers in the American League before the All-Star break. He tallied a 2.62 ERA and a .244 opponents' batting average against in 106.1 innings but fell off the proverbial cliff in the second half with a 6.38 ERA and a .292 OBA against in 73.1 innings.
His injury history, recent performance and age (he will be 35 years old during the 2018 season) all jump out and surely limited his value on the open market before the Mets signed him.
Still, there is a solid track record in place from before the injury problems arose, considering his 3.71 ERA and 1.27 WHIP in 2014 was his third season with a sub-4.00 ERA. In his lone season with the Mets, Vargas started two games, compiling a 12.19 ERA while going 0-1.
Vargas is not a top-of-the-rotation starter, but he provides valuable depth for a long season and helped the Royals reach the World Series in 2014 with a 3.52 ERA in three postseason starts.
If he rediscovers his first-half form from 2017, he could wind up being one of the offseason's more underrated additions.