Porcello's deal is pending a physical.
The 2016 American League Cy Young winner will earn $10 million, according to MLB Network's Jon Heyman, who also reports Porcello had multi-year offers but preferred a one-year deal.
Porcello struggled in 2019. The 30-year-old was 14-12 with a 5.52 ERA and 4.76 FIP in 174 1/3 innings for the Boston Red Sox.
During his Cy Young campaign in 2016, Porcello was a different pitcher. He was 22-4 with a 3.15 ERA in 223 innings pitched, including a 1.01 WHIP.
A right-hander out of Morristown, New Jersey, Porcello has been one of baseball's most durable starters since he debuted in 2009. He ranks ninth in innings pitched (2,037 1/3) during that time frame and has made at least 27 starts in every season of his 11-year career.