From the second inning on, the opposing team's pitcher recovered too, and it turned into a pitcher's duel.
Literal
2-inning after [from-以降], opposing-team [possessive-の] pitcher also recovered-[て form], pitcher-war became.
Baseball commentary style. 立ち直る ('to recover, regain composure, stand back up') is a compound verb from 立つ + 直る ('stand' + 'be fixed'). 投手戦 is a set term for a 'pitcher's duel' — a low-scoring game where both pitchers dominate. Note how Japanese uses 戦 (war, battle) productively to label competitive scenarios: 投手戦, 打撃戦, 攻防戦.