The phrase "unconvincing performances" refers to when someone's actions or behaviors don't seem believable or genuine. It means their actions seem forced or lacking in convincing effort. Full definition
Sterling now seems a priority target for City, who could do with more variety in attack after unconvincing performances from the likes of Samir Nasri and Jesus Navas out wide. (caughtoffside.com)
Credit to all three though, despite unconvincing performances in front of goal they've kept their heads and kept at it. (justarsenal.com)
However, Gatti was axed after a string of unconvincing performances by the host nation and Menotti decided to go with Fillol. (goalkeepersaredifferent.com)