"Ace sleeves" is a phrase commonly used to refer to someone's exceptional abilities or skills. The antonyms for this phrase could be "ineptitude," "incompetence," "mediocrity," or "mediocre performance." Those who lack natural skill might be considered an "unskilled" individual, while someone who carries little talent could be said to have "limited ability." Similarly, if someone is not considered a "master" at something, they might be called a "novice" or "amateur." Whenever someone does something poorly, they might also be deemed "ineffective" or "inefficient." In short, "ace sleeves" denotes mastery and success, while its antonyms suggest a lack of proficiency or expertise in a particular field.