ENGLAND captain Joe Root played down concerns over his side's misfiring top order after a comprehensive, series-levelling defeat to South Africa but kept the door open for changes ahead of the third Investec Test.

After kicking off his reign with a handsome victory at Lord's, Root saw his team humbled at Trent Bridge where they were skittled for 133 in 44.2 overs for a 340-run defeat.

Doubts over opener Keaton Jennings and Root's Yorkshire team-mate Gary Ballance are growing rather than receding with each innings, with the pair making 44 and 85 respectively in four knocks apiece.

Ballance's crease-bound technique has been exposed again on his third coming as a Test batsman, while Jennings' dismissal by Vernon Philander for three, was unedifying indeed.

Root provided some support for the pair in post-match presentation, but hinted their positions were not guaranteed for the Oval Test.

"No, I don't think it (the top three) is a concern. They just need some runs and to spend some time out in the middle," he said.

"I'm sure if they get the opportunity to do that in the next game they will go on and make big scores.

"We'll sit down with selection and make sure we're happy with what we have going into the next one."

Another player potentially looking over his shoulder is paceman Mark Wood.

The Durham player returned to the red-ball set-up after a two-year injury-enforced absence at the start of this series but has managed just one wicket for 197 runs in two Tests.

Bowling coach Ottis Gibson suggested he had experienced some discomfort in his heel – not his troublesome ankle – but Root is hoping that issue does not develop.

"It's been a tough week for Woody, really," he said.

"He worked really hard throughout the game and was unfortunate not to pick up many wickets but I can't fault his efforts, the way he's gone about it.

"In terms of fitness he came throuh quite well, so hopefully he's fit for selection for the next one."

England have been inconsistent as a Test side for an extended period and have often followed big wins with serious defeats, a trend that has now continued in the early days of the Root administration.

"It's been contrasting emotions in the last couple of weeks," he conceded.

"It's really important as a side we stay tight and don't mope or dwell too much on this. There's obviously areas to improve and learn quickly from, we have to take the positives out of it and come back really strongly at the Oval.

"We've got to learn quickly from that and, if we find ourselves in a similar position, we have to react better than we did here.

"Credit has to go to South Africa, who played very well over the course of the game, but we've got to make sure this doesn't happen again."