South Africa A surged ahead on the third day in Pallekele, bowling out Sri Lanka A for 326 and extending their lead to 280 with eight wickets still in hand.
Sri Lanka began the day on 253 for 4 but collapsed to lose their last six wickets for 63 runs. Fast bowler Quinton Friend finished with four wickets and was supported by Vernon Philander and Rory Kleinveldt, who grabbed two wickets each. Sri Lanka's overnight batsmen Kaushal Silva and Janaka Gunaratne looked good to take them close to the South African first-innings score but their dismissals put the visitors in control. Silva was run out for 84, while Gunaratne, who reached his century, fell for 122, bowled by Philander.
South Africa ensured they didn't squander their advantage. Dean Elgar Stiaan van Zyl struck half-centuries to add an unbeaten 110 and set the foundation for an imposing fourth-innings target for the hosts.