Root has been nothing short of incredible over the past fortnight, hitting 228 in the first Test against Sri Lanka and following up with an equally brilliant 186 on day three of the second Test.
His complete control in energy-sapping conditions was a sight to behold, taming the home attack in a 309-ball occupation that would not have looked out of place in the canon of local greats Kumar Sangakkara or Mahela Jayawardene.
Root looked set to carry his bat throughout the day's play only to fall in the final over, a victim of physical fatigue rather than technical error. After a couple of steps down the track the captain, who had been suffering from cramp and fatigue throughout the day, flicked the ball off his pads and was too stiff to get back in time as Oshada Fernando produced a direct hit from short-leg.
The rest of the England side managed 153 for eight between them, with Buttler's 55 the best of the rest as Sri Lanka held a potentially vital 42-run lead at stumps.
"It was a quite amazing innings, to back up his double hundred in the first Test and to show both the physical and mental application to do it again has been a masterclass in batting against spin," said Buttler.
"It's been an education for all of us watching on from the sidelines. We thoroughly enjoyed watching him and we were gutted for him to get out in that fashion at the end of the day.
"He certainly sits at the top table of cricketers in the world and the standards he sets himself and drives on to achieve is what makes him so good. That hunger to back up a double in the first game, to go and score another massive hundred just shows where he is at with his game.
"It's not just young players but older players and people watching from home can learn a lot from watching Joe Root bat against spin."
Buttler is one of the most enterprising batsmen England has ever produced, but keeps the majority of his improvised strokes for the limited-overs game.
Even he was impressed by the dazzling 'switch hits' Root began to unfurl as the innings progressed, briefly calling to mind Kevin Pietersen – a player he accelerated past as he moved into fourth in the county's all-time run-scorer's list with 8,238.
"There were some quite amazing shots really, which shows the confidence," said Buttler.
"I think he even played a little late cut left-handed as well. It's so great to watch and his skill level is second to none."
Root's efforts came in some of the most forbidding conditions around, with 32 degree heat amplified by punishing humidity and extended sessions. Every time there was a pause in play Root called for energy gels and bananas to replenish his reserves.
Buttler added: "Sri Lanka is as challenging as anything we face. I think that just adds to the magnitude of Rooty's innings really. Technically, tactically and physically it's an amazing effort.
"For the eight days of cricket we've had so far, he's been pretty much on the field the whole time. We have to not just praise the tactical and technical aspects of this game but the physicality and concentration to apply himself for so long."