Cole received a $3 million raise from 2017, when he went 12-12 with a 4.26 ERA.
One report earlier this week suggested the Astros were close to acquiring Cole, but Houston general manager Jeff Luhnow told the Houston Chronicle that a deal wasn't "imminent."
Cole has a 59-42 record with a 3.50 ERA in parts of five seasons with the Pirates. The No. 1 overall choice in the 2011 draft finished fourth in the National League Cy Young balloting in 2015 when he went 19-8 with a 2.60 ERA and made his lone All-Star team.
Mercer batted .255 with a career-best 14 homers last season, while Kontos compiled a 3.39 ERA in 65 appearances split between the San Francisco Giants and Pirates.
--Field Level Media