The Retired Emperor Uda said in his document called "Kanpyo-no-Goyuikai" (Emperor Uda's injunction), which was offered to the new Emperor, that Suenaga was so familiar with government affairs that he should be given an important position, as well as FUJIWARA no Tokihira, SUGAWARA no Michizane, and KI no Haseo.
宇多上皇が新帝に出した『寛平御遺誡』において、季長は「深熟公事（公務に精通した人物）」として、藤原時平・菅原道真・紀長谷雄とともに重用すべき人物として挙げられている。