Karasuno High School volleyball team in the anime "Haikyuu!!" typically handles unexpected injuries during matches by having a substitute player ready to step in immediately. The team's coach, Ukai, closely monitors the players' conditions and readiness to play, ensuring that injured players are promptly taken care of by the team's medical staff. The team also maintains a high level of communication and teamwork to adapt to any sudden changes in their lineup due to injuries.