To be matched against someone in a sports contest; to face an opponent in a match or bout.
次の試合で彼と立ち合うことになった。
I've been scheduled to face him in the next match.
相撲では土俵中央で力士同士が立ち合う瞬間が勝負の分かれ目だ。
In sumo, the moment the wrestlers meet in the center of the ring is often decisive.
柔道大会で同じ階級の選手と立ち合う。
He will face a competitor of the same weight class at the judo tournament.