He appeared in all but one of their league games, notching three tries along the way, earning the Scarlets' Management Player of the Season award in the process.
The 28-year-old, who has won 43 caps for Scotland, also captained the side several times in the absence of Ken Owens and Scott Williams.
And Hayward concedes that it was an easy decision for himself and the region's management to select Barclay as their player of the season.
"It was definitely a clear outcome who was the deserved winner of the award," explained Hayward.
"John is a true professional and work-horse on the field but is also the utmost professional off the field.
"He is a huge benefit to the coaching staff for the work he puts in and his leadership qualities in and around the group.
"He has played out of position for most of the season and is still right up there with quality performances every game."
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