On 2 August 2017, for the second consecutive year, the Mariners were knocked out of the FFA Cup by a state league team in the first round, after losing 3–2 to Blacktown City. During the 2017–18 A-League season, the Mariners were in the top four at one stage, but after a run of 11 games without a win the club dropped down the table. Okon resigned as manager with Central Coast in ninth entering the last four rounds of the regular season; Wayne O'Sullivan served as an interim manager following Okon's departure. With a six-game losing streak at the end of the season, the team finished last for the second time in three years. Former Brisbane manager Mike Mulvey was hired by Central Coast in 2018. In the first 21 matches of the 2018–19 A-League season, the Mariners won only once. Mulvey was replaced as manager by Alen Stajcic, the former head coach of the Australia women's national team. Despite two wins in his six games as a caretaker manager, the Mariners were unable to avoid finishing at the bottom of the table again. Stajcic was given a three-year contract after the season.