South Africa cruised to a 139-run win over Ireland in the teams' first ODI in Abu Dhabi, with Lizaad Williams tearing through their opponents' batting order. (More Cricket News)

The Proteas approached Wednesday's contest reeling from a shock T20I defeat to Ireland on Sunday, with Ross Adair's maiden international century ensuring the two-match series ended 1-1.

There was not to be a repeat in the 50-over format, however, with Ireland's batting order collapsing after Ryan Rickelton (91) and Tristan Stubbs (79) guided an otherwise shaky South Africa to 271-9.

The Proteas started miserably by losing three wickets for 39 runs, Mark Adair taking two of them on his way to figures of 4-50.

But opener Rickelton stayed cool while the wickets tumbled around him, lasting 102 deliveries and allowing Stubbs to join in on the act with comfortably his best ODI score, dragging South Africa to a respectable total.

Ireland might have harboured hopes of a successful chase, but Paul Stirling's fourth-ball dismissal for just two runs set the tone, and a spate of four more wickets in the space of six overs dropped Ireland to 61-5.

Williams finished with figures of 4-32 from his 10 overs for the Proteas, who needed just 32 overs to finish off the tail and bring some much-needed positivity to their tour of the United Arab Emirates, which started with an ODI series loss to Afghanistan.

Data Debrief: Williams wins it?

Rickelton and Stubbs carried South Africa to a score they were capable of defending despite no other batter scoring more than Bjorn Fortuin's 28 – seven scored 13 runs or fewer.

But it was Williams who made sure of the victory, taking three of the first four wickets to leave Ireland in a tailspin, then going on to record the best figures of his young ODI career.

In none of his previous five ODIs had Williams managed more than two wickets, while his 32 runs conceded were also his fewest in the format.