If a creature with vigilance is untapped after attacking, can it block during the same combat?

Vigilance (CR 702.20) allows a creature to attack without tapping, meaning it remains untapped after being declared as an attacker. However, being untapped is not the only requirement to block — a creature that has already been declared as an attacker in the same combat step simply cannot also be declared as a blocker.

CR 509.1a specifies that only creatures the defending player controls that are untapped and were not declared as attackers may be declared as blockers. Since the vigilance creature was declared as an attacker in the same Declare Attackers step (CR 508), it is ineligible to block regardless of its tapped status.

Additionally, the Declare Blockers step (CR 509) occurs after the Declare Attackers step within the same combat phase, so there is no mechanical window for a creature to participate in both declarations in a single combat.

Concrete example: You attack with a 3/3 creature with vigilance. It stays untapped. Your opponent then casts a removal spell during the Declare Attackers step. Even though your creature is untapped, it cannot be declared as a blocker when the Declare Blockers step arrives — it is committed as an attacker for this combat.

In short, untapped status is a necessary condition to block, but not a sufficient one. A creature cannot serve as both an attacker and a blocker in the same combat phase under any circumstances.