Even after signing Andrew Miller and letting David Robertson walk, Brian Cashman has admitted that the bullpen is still not a finished product. As we've seen with the Royals bullpen last year, the more elite relievers you have, the shorter the game becomes. Cashman says that that Miller, Dellin Betances, and the newly acquired Justin Wilson give them three pitchers that can be relied on in the back of the bullpen. He also said that they were still looking around at the free agent market and for relievers in a trade.
Romo used to be a a very well-regarded closer for the Giants, but last year proved to be a disaster for him. At the age of 31, he pitched to a fine 3.72 ERA and 3.94 FIP, but his late-inning struggles turned him into a negative-WAR player. Despite this, Romo will likely be looking for a multi-year commitment, maybe two years, so he can rebuild his value and still make a good amount of money. Ultimately, he's likely a poor fit because the Yankees shouldn't be giving him that kind of deal and Romo is unlikely to get many save opportunities.
It's highly likely the Yankees either sign or trade for another reliever before everything is said and done, but Romo might not be the right one. If they can get him on a one-year deal, at max with a team option, then it might be a good idea to have the seventh, eighth, and ninth locked down, but still, that's no sure thing. Should the Yankees pursue Sergio Romo?