The result put this month’s African Champions League runners-up top of Group F after Borussia Dortmund were held 0-0 by Fluminense earlier in the day.

It was also a first victory for an African side at the new-look 32-team tournament in the US after Egypt’s Al Ahly drew their opener while Esperance of Tunisia lost to Flamengo yesterday.

Rayners’ goal came nine minutes before halftime at the Inter & Co Stadium in a match that was delayed by just over an hour due to the threat of lightning in central Florida.

The teams had come onto the pitch to start the match before French referee Clement Turpin ordered them back to the change rooms as a precaution.

Rayners had two other first half strikes ruled out after VAR checks – one for handball and the other inches offside.

The effort which counted was a well-worked effort with Sundowns’ Brazilian playmaker Lucas Ribeiro slipping a pass through the Ulsan defence for the striker to poke into the net.

Sundowns could have been ahead inside the opening 20 seconds after some slick passing set up a chance for Ribeiro but his effort was blocked.

It set the tone for almost total dominance by Sundowns, who had more than 70% of possession, though their passing game was too pedestrian at times and they were wasteful in front of goal.

Ulsan looked for chances on the counter and had their best opportunity in the fourth minute after a quick break but the Korean club’s Brazilian forward Erick Farias missed with the goal at his mercy.

Ulsan were rarely on the front foot but did have two opportunities that Sundowns scrambled off the line.