This is the 2481st most frequent Japanese word.
先発
"Starting; first to go; starting player; starting pitcher."
In this context, '先発' (senpatsu) refers to the starting pitcher, denoting a player who starts the game in this role.
彼は今日の試合で先発ピッチャーとして登板します。
He will take the mound as the starting pitcher in today's game.
Here, '先発' (senpatsu) is used to mean introducing something first, indicating initial deployment or launch.
新製品を先発で市場投入する計画があります。
There is a plan to launch the new product to the market first.
In this scenario, '先発' (senpatsu) implies an advance group or team that precedes the main party to make preparations.