Opener Herschelle Gibbs poses a selection dilemma as South Africa prepare to take on Sri Lanka in their must-win third one-dayer on Wednesday.

The 30-year-old has been a frequent match-winner for the tourists over the years, scoring 12 centuries and 19 fifties in a 151-match career, but his form has been wretched in Sri Lanka.

Gibbs has scored 11 runs in four innings and looked awkward at the crease since battling back to full fitness after an ankle injury forced him out of the first Test earlier in the month.

South Africa are desperate to win after conceding an early 2-0 lead in the five-match series and that has forced the selectors to consider Gibbs' place in the team.

"Herschelle (Gibbs) is a world-class player and has been a proven match-winner time and time again for South Africa," skipper Graeme Smith told reporters.

"It is very difficult to leave out a man of his calibre, as we know he could go out any day and win the game in 30 overs, but it is something that has been up for consideration with the selectors," he added.

Martin van Jaarsveld, a 30-year-old with nine caps, battled hard against Sri Lanka's spinners in the Test series and could be called up if Gibbs is dropped.

"We have options with a few guys that can bat in the top order and Martin (van Jaarsveld) is the most likely to play if we leave Gibbs out," said Smith.

But wholesale changes have been ruled out: "I don't expect too many changes. We have been playing our best team and will give them one more go."

South Africa are taking heart from their recovery from a similarly dire situation against Pakistan last October, when they won 3-2 after losing the first two games.

But Smith's team are stuck in a losing run having lost their last seven successive one dayers in New Zealand and Sri Lanka -- the second longest run of defeats in their history.

"We have fallen out of the winning habit and we have been a little tense in the crunch situations. We have spoken about the need to relax so that we can finish games off more ruthlessly."

Sri Lanka's only selection dilemma is whether to play two or three seamers. Fast bowling all rounder Farveez Maharoof and spinner Rangana Herath are competing for the final place.