In what has been a relatively more dramatic session of play, South Africa picked up two scalps in the post Lunch period, and also almost accounted for the wicket of Joe Denly, to leave England at 117/2 at Tea on the opening day of the third Test.
It was a massive statement from the 29-year-old, who was told in no uncertain terms by Proteas leadership that his way back into the national set-up would be through scoring runs at franchise level and in the 4-Day Franchise Series.
Sibley followed his maiden Test century in Cape Town with 36 and Crawley made his highest Test score of 44 to give England a solid start but both gave their wickets away in the afternoon session, surrendering the chance to play the big innings that would be so important at the start of their careers.
Sibley fell soon after Lunch as he clipped a Kagiso Rabada delivery on the middle and legstump line to the fielder at backward short leg. Crawley, however, wasn't adventurous with his shot-making and managed to last more than an hour into the second session.
Left-arm spinner Keshav Maharaj conceded only 22 runs in 19 unbroken overs from the northern end of the ground, enabling South African captain Faf du Plessis to rotate his four fast bowlers from the southern end.
Joe Denly was leg before to Maharaj when South Africa successfully sought a review which showed a ball headed for the stumps had hit pad before bat, while Root was beaten and bowled by a fast delivery from Rabada which hit the top of his off stump.
With the four-match series tied at 1-1, batting first appeared to be a considerable advantage on a pitch which had a fair covering of grass but which offered no help to the bowlers.
South Africa picked new cap Dane Paterson as a specialist fast bowler in place of all-rounder Dwaine Pretorius.
England had earlier made one enforced change to their line-up with Mark Wood returning to first-class action for the first time in 11 months in place of injured seamer James Anderson.
It was the sixth successive Test toss lost by Du Plessis.
Paceman Jofra Archer will stay on tour as England hope to get him fit for the last Test against South Africa in Johannesburg next week, officials say.