Vernon Philander will work on his conditioning ahead of a packed home summer scheduled to feature 10 Tests, including two four-match series against India and Australia, for which South Africa want him to be fully available.

Philander struggled with a comeback from an ankle injury and a viral ailment in the first and third Tests in England respectively and then sat out the fourth with a back concern. He came under severe criticism from his former captain Graeme Smith and his current skipper Faf du Plessis has also weighed in, urging Philander to focus on his fitness.

"It's fair that you need to play a lot of cricket for your country and be available for selection and Vern accepts that," he said. "If you're only playing one or two Test matches and then off for one or two… there have just been too many times when we as a team go, gulp, 'Vern might be injured again'. So he's taken it on board from a fitness point of view.

"We have important series coming up, not that we play series that are not important, but India and Australia at home, it's eight Test matches and he needs to be fit to get through all of them."

Philander's value to South Africa was underlined in the second Test when he turned in a Man of the Match performance at Trent Bridge. South Africa were depending on him as they sought the series lead at The Oval and though he bowled well on an opening day interrupted by toilet breaks, the rest of his participation was limited. He spent a second night in hospital and though he returned to bat, could not bowl as much as needed in the second innings in conditions that would have been perfect for him.

Then, just as South Africa thought they would have Philander back for their must-win game at Old Trafford, he pulled up with back spasms, which left Smith fuming and du Plessis frustrated.

"The last I spoke to you, I said he's just got to do a small fitness test but he'll be fine. So when he woke up with a stiff back the next morning it was frustrating," du Plessis said. "For us to have competed and to win Test matches we needed Vern, you need your best players. Duanne bowled well this game but Vern is one of the best in these conditions, probably the best in seaming, swinging conditions which has been the case in all four Test matches, so not having him here was very frustrating and disappointing."

Philander played in all 11 Tests - two against New Zealand at home, three against Australia away, three against Sri Lanka at home and three against New Zealand away - prior to this series, but he struggled with injury in the early part of his career. He had injuries in three of his first four series - a knee, back and hamstring problem - before tearing ankle ligaments in India in November 2015 that kept him out of action for nine months. Philander has admitted it took time for him to fully trust the ankle again and it would not have helped that he injured the other one in the lead-up to this series.

Given that he only plays one format at international level, Smith pointed out that Philander does not always have the benefit of a team trainer to put him through his paces. He has had to take that responsibility for himself and du Plessis said Philander has committed to doing more. "It is a challenge for Vern because it's happened too often that he doesn't play a full series. I've spoken to him about that and he's accepted the challenge and that he needs to improve that."

Firdose Moonda is ESPNcricinfo's South Africa correspondent