at the top of (one's) game
At one's best or most skillful. I can't believe I got the hardest question right. I'm really at the top of my game today! I think their quarterback is at the top of his game this year—I doubt he'll be able to replicate these stellar stats next season.
at the top of one's game
Fig. good and as good as one is likely to get. (Usually of sports.) I guess I was at the top of my game last year. This year, I stink.