Roy underwent concussion test following the blow and continued batting after few minutes.
"There was plenty of analysis afterwards saying we were pushing too hard at the ball, but I can honestly say as someone who'd played a lot in England, I was trying to smother away movement I knew to be there".
England named an unchanged squad on Monday for this week's third Test against Australia at Headingley, with the injured James Anderson continuing his bid to return later in the series.
Roy passed tests at the time of the incident but will be checked again, with county team-mate Ollie Pope, who is now 176 not out overnight against Hampshire in the County Championship, on standby.
De Villiers, who retired from worldwide cricket in 2018, played 114 Tests for the Proteas and scored 8 765 runs with an average of 50.66. Though independent doctors will surely become mandatory as the protocol is refined in years to come, the arrival of concussion substitutes to usher in the Test Championship era already has its landmark case.
But no sooner were critics lashing England's lacklustre showing than the hosts rebounded, taking three wickets for three runs to turn the game back in its favour.
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Australia's head coach Justin Langer has told his bowlers not to let their egos draw them into a battle of the bouncers at Headingley, after Steve Smith was ruled out of the third Ashes Test with concussion.
"As it stands we fully expect him to be fit and ready for (Thursday)".
Fast bowler Jofra Archer, who replaced Anderson in the second test, claimed five wickets on debut at Lord's and bowled consistently over 90 miles per hour.
JASON ROY belongs at the top of the England order in Joe Root's eyes, despite reservations expressed by Trevor Bayliss. But I feel Jason can have a real big impact at the start of an innings. "It hasn't happened yet but we fully expect him to be able to come in and do that". "We think we've got the best seven batters available to us at the moment".
"I'm sure the bouncer will still be part of every bowler's armoury, if it helps us get batsmen out then we'll use it, otherwise we'll keep sticking to the plan". "In 2010, the European Central Bank provided the PCB facilities to host Australia in a two-match Test series", Khan said. Broad added Usman Khawaja after play resumed in the afternoon, a loose delivery down the leg side clipping the edge after a succession of brilliant balls from the veteran seamer had failed to do the trick.