Manchester - South Africa captain Faf du Plessis lamented Vernon Philander's lack of fitness after his side's Test series loss to England.
The hosts' 177-run victory in the fourth Test at Old Trafford on Monday saw England secure a 3-1 triumph in Joe Root's first series as skipper.
But a four-Test contest played largely in the kind of overcast conditions in which Philander thrives might have been a very different story if the key seamer had remained fully fit throughout.
The 32-year-old appeared poised for a brilliant campaign after taking five wickets and making scores of 54 and 42 in a man-of-the-match display during South Africa's 340-run series-levelling win in the second Test at Trent Bridge.
But he was struck down by a mystery virus that reduced his effectiveness in the third Test at The Oval and Philander did not even make the team at Old Trafford because of a back problem.
It was not the first time Philander, whose overall Test record of 171 wickets in 46 Tests at an average of 22.45 is outstanding, had failed to complete a series and du Plessis's patience appears to be wearing thin.
"For us to have competed and to win Test matches we needed Vern, you need your best players," the Proteas captain told reporters following South Africa's first Test series loss in England since 1998.
"Duanne (Olivier) 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.
"The last I spoke to you (the media) 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," the middle-order batsman added.
"It is a challenge for Vern because it's happened too often that he doesn't play a full series," du Plessis explained. "I've spoken to him about that and he's accepted the challenge and that he needs to improve that.
"There have just been too many times when we as a team go (gulp) 'Vern might be injured again'."
Looking ahead, du Plessis said: "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."