Holecek reported to the perennial Super Bowl bound Bills rookie camp in April 1995. He played six seasons with the Bills, averaging over 14 starts his last three seasons. Holecek flourished as an inside linebacker in Phillips' defensive 3-4 system. He also briefly played middle linebacker in a 4-3 alignment when injuries caused Coach Phillips to switch defenses mid-season. John emerged as a defensive stalwart and on-field coach for the Bills, notching an incredible 414 tackles from 1998-2000 and became known for his technique and football acumen.