Ben Westwood faces ban for headbutting Wigan Warriors' Morgan Escare
Greenwood, only just back after a two-game absence, was placed on report by referee Ben Thaler for a late challenge on Blake Austin during Friday's game, which Warrington won 25-12.
But the RFL's match review panel viewed the incident and decided it was a "reckless" strike, and classified it as a Grade A offence, which carries no further punishment.
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Hide AdWestwood, though, is facing a suspension after being charged with a Grade D head-butt on Escare, which led to him being sent off. He will learn his fate when he appears in front of the RFL's disciplinary panel tomorrow. A Grade D offence usually carries a suspension range of three to five matches.
Wigan's Dan Sarginson and Willie Isa were also sinbinned, as well as Warrington's Dec Patton, during a heated derby.
Sarginson was also issued a Grade A charge for "reckless" striking with arm, and faces no ban.
Warriors' Taulima Tautai is currently sidelined because of suspension. He has served one game of a three-match ban while fellow prop Oliver Partington will sit out this weekend after being given a one-match suspension while playing for dual-registration club Swinton last week.