Manly ended 2026 in ninth place, two wins short of the finals, after taking only two victories from its final nine regular-season games.
Foran told SEN's The Run Home with Joel and Fletch he believed the Sea Eagles had underachieved.
"In the sense that when I look back on the season, I felt like we underachieved, to be completely honest with you.
The club had started with three consecutive home defeats under Anthony Seibold before he left and Foran took charge.
Foran's first game brought a 52-18 win over the Dolphins in Redcliffe, and Manly climbed to sixth by Round 17.
Foran said the side lost six straight, struggled to manage its slump and was affected by key injuries.
He said the team's effort and commitment gave Manly something to build on for 2027.