expression, noun
pro among pros; best of the best; top tier
Emphatic expression meaning someone who is exceptionally skilled even among professionals; often used in sports, business, or creative fields.
彼はプロ中のプロだから、どんな難しい仕事でも任せられる。
He's a pro among pros, so you can trust him with any difficult job.
あの選手はプロ中のプロと言われるだけあって、プレッシャーの中でも冷静だ。
That player is called the best of the best, and sure enough, he stays calm under pressure.