Jason Roy's swashbuckling batting helped opening partner Alex Hales return to form in the first ODI in Bloemfontein, says Nick Knight.
Hales bounced back from a run of low scores in the Test series victory over South Africa to club 57 from 47 balls in England's 399-9, their second highest ODI total in history.
However, Roy (48 from 30) played the aggressor in the pair's first-wicket stand of 68 in 7.4 overs and Knight says the Surrey star is fast becoming a key man for his country.
"Combination is the key for Hales and Roy," Knight told Sky Sports after England beat South Africa by 39-runs on the Duckworth-Lewis method to take a 1-0 lead in the five-match series.
"Hales would have felt a little nervous having not scored runs in the Test matches but those nerves would have dissipated with Roy getting into his groove so quickly.
"That helped Hales feel his way in and not play a rash shot and possibly lose his wicket early."
On Roy not converting his start into a fifty or a hundred, Knight added: "I wouldn't be having a word with him, I would just wind him up and let him go.
"There may be a mild concern that it is just 48 and not a century but he got the team off to a flyer and settled Hales and the dressing room down - that's his job so I would leave him alone."
Joe Root (52 from 58) and Ben Stokes (57 from 38) matched Hales in posting half-centuries but Jos Buttler was England's key man with the bat, biffing 105 from 76 balls, his fourth ODI ton.
Buttler came out to bat ahead of captain Eoin Morgan at No 4, just as he did when cracking 116 from 52 deliveries against Pakistan prior to Christmas in his previous ODI.
"It was selfless from Morgan, who is in very good form, and astonishing from Buttler," said Knight, after Buttler drilled 11 fours and five sixes.
"Buttler almost has the complete game, with the craft and the deft touches as well as the power, and I don't really know where you can bowl to him."
Watch the second ODI between South Africa and England from 7.30am, Saturday, Sky Sports 2.