De Wet had an injection on the fourth day and was only able to bowl eight overs of medium pace on the final day as England survived with nine wickets down. Parnell, who was part of the squad for the first Test before being omitted, is the logical replacement and has impressed during his one-day and Twenty20 career and already has two five-wicket hauls in ODIs
"We don't know how Friedel de Wet will turn out, his chances don't look very good but we will know more by Monday," Mike Procter, the convenor of selectors, told Cricinfo and he added de Wet's injury seriously hampered South Africa in Cape Town. "A crucial moment in the game was the injury to Friedel which he picked up in the first spell he bowled. That held us back a bit."
Parnell's recall also seemingly spells the end of Makhaya Ntini's Test career after he was dropped for the third Test although Procter wouldn't be quite so final. "The door is never shut on anyone," he said. "If he comes back and performs well of course he can get back, but the chances are not great because he hasn't done very well domestically."
Ntini played for his domestic side, the Warriors, on Friday evening but only managed 1 for 41 from six overs in an MTN40 match at Centurion Park and has been widely tipped for a Kolpak deal in county cricket.
Despite South Africa pulling up one wicket short of victory for the second time in the series, Procter was buoyed by the team's improvement following the innings-and-98-run hammering in Durban.
"The performance was tremendous," he said. "We outplayed England, scored a huge amount of runs and were able to declare which says it all. We came very, very close. We have been one ball away from two different results [in the series] and I think we played much better.
"In both games nine wickets down came about very quickly, England collapsed and lost wickets right at the end. It wasn't as though we had a long period to bowl when there were only a few wickets to go."
Andrew McGlashan is assistant editor of Cricinfo