ɐ dᵻfˈɛnsɪv sˌʌbstɪtˈuːʃən ɪnðə ɡˈeɪm ʌv bˈeɪsbɔːl əkˈɜːz wɛn ɐ kˈɜːɹəntli nˈɑːnplˈeɪɪŋ plˈeɪɚɹ ɪz plˈeɪst ˌɪntʊ ðə fˈiːld ɪn plˈeɪs ʌv ɐnˈʌðɚ plˈeɪɚ, tˈɪpɪkli dˈuː ˈiːðɚ tʊ ˈɪndʒɚɹi ɔːɹ ðɪ ɐpˈɪɹəns əvə pˈɪntʃ hˈɪɾɚ.
A defensive substitution in the game of baseball occurs when a currently non-playing player is placed into the field in place of another player, typically due either to injury or the appearance of a pinch hitter.