The Blues forward fronted the AFL tribunal on Tuesday night and pleaded not guilty to intentionally striking North Melbourne star George Wardlaw in Carlton's Good Friday defeat.
Hayward hit Wardlaw late with a swinging arm to the midriff as he kicked North into attack during the third quarter at Marvel Stadium.
The incident was graded as intentional conduct, medium impact and body contact.
Carlton argued the impact should've been graded as low and the conduct characterised as careless.
While it took an hour of deliberation, the tribunal upheld the charge.
"The conclusion that this was an intentional strike is, on the evidence, irresistible," tribunal chairman Jeff Gleeson KC said.
"The only act with which Hayward's swinging fist was consistent was that of a strike."
Hayward, who left Sydney as part of the blockbuster Charlie Curnow trade, had denied he had set out to strike Wardlaw.
"My intention the whole time was to put pressure on the ball," Hayward said.
"I couldn't see where the ball was at the time of the impact.
"I just stand by that my intention was to put pressure on ... to put him off balance by making contact.
"The first point of contact was actually his arm, so that might have swung him, maybe forced him to move his hips and disrupt the kick."
Asked in cross-examination if he would repeat the action if he had his time again, Hayward said: "Yes".
The AFL argued Wardlaw was not braced for contact but "vulnerable, unguarded, unprepared", noting the point of contact was the stomach.
Hayward's clenched fist was also taken by the AFL as a sign of a deliberate strike.
But Blues lawyer Chris Townshend KC argued that this year's rule change - which mandates that intentional strikes will at minimum be classified as medium impact - was meant to be applied to off-the-ball incidents, rather than in Hayward's instance.
"Accounting for all inflation in the world over the years," Townshend KC began.
"I doubt there's anyone in their lounge room - even particularly with the big, beautiful screens they have these days, all around the country - who would say that swinging an arm out, across a body, in circumstances where the player gets up, takes the kick, gets the 50 (metre penalty), on they go, happy days, should ever be described as more than low impact."
Hayward's suspension is another blow for the struggling Blues, who are already without vice-captain and first-choice key defender Jacob Weitering (concussion).
Carlton will be out to rectify a 1-3 start to the season after a series of second-half meltdowns, with under-pressure coach Michael Voss in the final year of his contract.
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