Cape Town - Imran Tahir returned to his very best form and then Faf du Plessis hit his 11th century in the format as the Proteas coasted to an eight-wicket victory over Sri Lanka with 11 overs to spare in the opening One-Day International at the Wanderers Stadium in Johannesburg on Sunday.

In terms of ICC World Cup preparation the Proteas ticked one very important box and that was their achievement in taking six wickets for 154 runs in the middle power play. This was after they had taken 2/59 in the opening power play and made certain that Sri Lanka would not be able to launch any kind of assault in the final one. 

Tahir (3/26) made the key contribution, taking all his wickets in the middle power play. He struck early with his fourth delivery to end an important third wicket stand of 76 between Kusal Perera and Oshada Fernando and then did the same in his second spell when he got rid of two batsmen well set in Kusal Mendis and Dhananjaya de Silva to put an end to the other significant stand of 94 for the fifth wicket. 

At one stage it looked as though Sri Lanka would go on to somewhere near the 300-run mark which is the benchmark for any side in this format but instead they were dismissed for a well below par total of 231 and failed to bat out their 50 overs. 

Lungi Ngidi, making a successful return from injury, also took 3 wickets (3/60) while there was a debut wicket for Anrich Nortje and a 99th wicket in this format for Kagiso Rabada. 

Sri Lanka did themselves no favour with their running between the wickets which accounted for the other two dismissals. 

Mendis (60 off 73 balls, 5 fours and a six) was the only visiting batsman to go past the half-century mark although several others threatened to do so. 

Whatever chance Sri Lanka had of staying in the contest effectively disappeared when Du Plessis was dropped on 32. He had hit his three previous deliveries from Thusara Perera for boundaries and the psychological impact for that lost opportunity must have been severe. 

It opened the way for Du Plessis (112 not out off 114  balls, 15 fours and a six) and Quinton de Kock (81 off 72 balls, 11 fours) to overcome the potential threat posed by the Sri Lankan mystery spinners and lay the foundation for victory. Their partnership was worth 136 in 22 overs before Du Plessis and Rassie van der Dussen finished off the job. 

The latter continues to go from strength to strength and has now made 273 in 6 matches and has only been dismissed twice. 

Du Plessis was named Momentum Man of the Match. This was his third century against Sri Lanka and his second at the Wanderers. It was also his career best at this venue. 

The second ODI takes place at SuperSport Park on Wednesday (13:00 start).