Sources told The Athletic that the deal is believed to be for three years.
Happ, 36, posted a 2.69 ERA and a 7-0 record in 11 appearances last season for the Yankees. He joined the Yankees in a trade from the Toronto Blue Jays in July. Happ was granted free agency in October. He posted a 4.18 ERA and a 10-6 record in 20 games with the Blue Jays in 2018 before the trade.
The left-handed pitcher a 3.90 ERA and a 109-82 record during his 12-year Major League Baseball tenure.