Santiago signed a minor-league deal with an invitation to spring training with the Mets on Saturday, Matt Ehalt of The Bergen Record reports.
Santiago spent 2018 with the White Sox, starting seven games and appearing in 42 more in relief. His 4.41 ERA and 22.4 percent strikeout rate are respectable, but he walked 13.0 percent of opposing batters and finished with a 5.09 FIP. His FIP hasn't been below 5.00 since 2015. He'll likely be battling for a long-relief role in New York but could wind up making a handful of starts if things break his way.