Coach Gary Kirsten has called on the South African public to support the out-of-form Graeme Smith, rather than heap pressure on the left-hander as he searches desperately for runs.

Smith's position in the one-day side has come under scrutiny during the series against Sri Lanka, during which he has scored just 36 runs in three matches.

South Africa sport an unassailable 3-0 lead in the series, but rather than relieving Smith of some pressure, the success of those around him appears to have increased it as Proteas fans question the Test skipper's place in the side.

Smith stepped down from the one-day captaincy last year, but while this makes him more vulnerable to the axe, Kirsten suggested that he deserved some time after everything Smith has done for South Africa.

"He is going through a tough time and he has acknowledged that. There's a lot of pressure on him and he knows he needs to perform," Kirsten said.

"We've got to support him as much as we can in the team. He deserves a little bit more than others because of the service he has given to this country as a leader. He has been the stand-up guy, the face of the team for many years and he needs support."

With the series sewn up, Kirsten confirmed that he will continue to rotate in order to build a larger squad of players that can perform whenever they are called upon.

"We were always planning to experiment throughout the series and it's important that we develop and grow players so that we have a squad of 16 or 17 players we can pick from at any time," he said.

"It allows us to rotate better, and rest players, because we know that the guys coming in have got the experience and they're equally as good.

"The exciting thing is that there is competition for places and that's important - not only in the one-day unit, but also in the Test unit people are competing for places."

Kirsten highlighted the middle order, which has been rotated in each of the three games, as key to one-day success.

"For me, four, five, six and seven are the crucial batting positions in many respects in one-day cricket because those are your closers," he explained.

"I just want to be comfortable with who our best closers are in the team, so we're going to mix it up and rotate it a bit.

"Also the left-hander/right-hander combination plays a very important role, so there will be great flexibility within that space."

Kirsten also praised AB de Villiers for the way he has embraced his new role as captain and wicketkeeper in the one-day format.

"AB's been quite creative and that's good for us," Kirsten said.

"He's also given the bowlers responsibility, wanting to know what fields they want and what they're planning to do in an over.

"He brings a certain freshness to the role, but it's tough being both captain and keeper in one-day cricket, so we're mindful of that, but all credit to him."