#1 J.A Happ
Re-signing Happ should be a top priority for the Yankees. The lefty who was traded from Toronto to New York last season has had a fantastic regular season donning the pinstripes. With a record of 7-0 starting for the Yankees and an impressive ERA of 2.69, there's no doubt that Happ is a fine fit in the Bronx.
With Severino and Tanaka confirmed to return in 2019, JA Happ is an ideal 3rd or 4th pitcher depending on who the team signs in free agency. Also, Happer has already played in the Bronx and finding a player who doesn't need time to adjust to the new team is a matter of millions in the player market and hence this should be a no-brainer.
The only problem is his age. The former Blue Jay is 36 years old and it's quite a possibility that his performance can't remain the same and starts to worsen. That being said, a two-year contract with a good financial commitment should be good enough to bring back Happ to the Bronx.