JP Duminy may not be able to keep his place in South Africa's Test XI after the returning captain, Faf du Plessis, conceded Duminy was under pressure due to poor form. That observation is vastly different from the support du Plessis had offered in the recent past, often saying Duminy looked at his best in training and it was only a matter of time before he translated that into match-day performances.

Now, after eight innings without crossing 40, du Plessis has been forced to admit Duminy is not doing enough. He made 15 and 2 in the first Test at Lord's, with his dismissal on the stroke of tea on day four particularly culpable as South Africa slipped to a 221-run defeat.

"JP will be the first guy to say he knows he needs to score runs for this team and it's no different for anyone else," du Plessis said. "He is desperate to do well as anyone in that position. You want to try and score runs every time you go out that. He knows at the end of the day that it's about runs. He understands that if it has to come to a position where there is someone else that needs to be looked at… he will be the first to acknowledge [that]. He is a crucial part of our senior player group and he will always put the team interests above himself so yes, he will be the first to acknowledge that."

With du Plessis back in the squad after missing the first Test for the birth of his first child, one option would for him to slot straight back into the team in Duminy's place but the captain said South Africa will consider a few other things. Kagiso Rabada is suspended from the Trent Bridge match for ICC code of conduct violations and South Africa may look at playing both allrounder Chris Morris and reserve quick Duanne Olivier to make up for his absence. In that case, Theunis de Bruyn would have to miss out, with du Plessis coming in for Duminy.

"With losing KG - do you look at possibly playing a four-seam attack because you are losing quite a high-quality bowler? That's means there would be a batsman that will miss out," du Plessis said. "That's one option."

Either way, du Plessis seemed to suggest that de Bruyn, who scored 48 in the first innings in what was just his second Test, has moved up the queue and possibly ahead of Duminy for the rest of this series. "You can look at someone like Theunis de Bruyn who has played pretty well this game - standing up at Lord's and it's only his second Test match. He was solid in that first innings. He played well," du Plessis said.

The form of the middle order was the only positive South Africa's batting could take from the Lord's Test after the top four let them down yet again. Temba Bavuma, Quinton de Kock and Vernon Philander all scored half-centuries and du Plessis would like to see one of them in particular go on to convert that into something bigger.

"Temba has once again been consistent," du Plessis said. "But now, something Temba needs to work on is making sure he converts those starts. He is playing brilliantly but he knows that fifties don't win us matches. The difference between the two teams is that one guy scored 190. That changed the outcome of the game."

Bavuma has scored three fifties in his last four Tests but only has one hundred in his short career, against England in January 2016. Having to constantly bail the top order out may be a handbrake for him, however, and du Plessis stressed that the top two must come good. Dean Elgar got a start with a half-century in the first innings at Lord's and du Plessis was confident Heino Kuhn, who was unconvincing on debut, will show his experience at some stage.

"Heino Kuhn is not a young guy anymore but he is new to Test cricket," du Plessis said. "I don't think everything is supposed to be a fairytale where you just rock up and score two hundreds in your first game. Ask Dean. He got a pair in his first game. It's about character and how you stand up to that. This will be good. It will make him stronger."