(someone/something) is past (his/her/its) prime

Something that is "past its prime" is no longer as strong as it used to be.

You can use "past its prime" to talk about people who aren't as healthy and strong as they were in the past. You can also say that a country or city is "past its prime" when it is used to be economically strong but is now poor and run-down:

People say that Detroit is long past its prime, but some still hold out hope that the city will revive itself.

If something is still young, strong, and healthy, you say that it is "in its prime":

In his prime, he was one of the strongest players in the league.

at (his/her/its) peak

The phrase "at its peak" is very similar in meaning to "in its prime". But the "peak" of something is the very highest level of performance, while the "prime" is a longer period of generally good performance. An athlete's "prime" might last several years, but their "peak" might only be a single season.

The "peak" of a mountain is the very top. It's the highest point on the mountain. So you can imagine that, if a person's skill or strength was recorded on a graph, the highest point of the graph will look like the peak of a mountain. This is why we call this point a "peak".

Some other phrases that include "peak" used in this way include:

• To "reach a peak" means to gain the highest level that you've ever achieved at something.
• "Peak performance" is the highest level a person is able to perform at.
• "Peak production" is the fastest speed that a factory, industry, farm, etc. can make something.

a great player

The adjective "great" is often used to describe "players" in sports. Other common adjectives used with "player" include:

a star player

a valuable player

a dominant player