Keita fully established himself in the starting lineup in the 2016–17 season, scoring his first goal of the season in Serie A matchday 6 against Empoli at home. On 6 March of the following year, Keita made his 100th Serie A appearance in the 2–0 win at Bologna. Later on 23 April, Keita scored his maiden hat-trick, contributing in Lazio's 6–2 thrashing of Palermo, taking his tally up to 11 goals, reaching double figures for the first time in his career. He completed the hat-trick in five minutes, making it the fastest hat-trick scored in Serie A since 1974–75 season. One week later, in the Derby della Capitale against Roma for the matchday 34, Keita scored a brace, as Lazio won 3–1, the first win in the league against them since November 2012. He also become the first Lazio player to score a brace in the derby since Roberto Mancini in 1998–99 season.