Adelaide had marginally shaded the Sky Blues across an even battle at Coopers Stadium,and it finally broke open for the hosts when Yengi was brought down by Luke Brattan in the 74th minute.
Confusion reigned in Sydney’s defensive box after captain Alex Wilkinson and left-back Joel King took each other out while challenging for a loose ball,which Yengi then pursued – blindsiding Brattan,who struck the 22-year-old as he burst through.
Referee Shaun Evans took a few moments to dwell on the incident before blowing his whistle,with Goodwin stroking his penality past Andrew Redmayne for his fourth goal in five games since re-joining United mid-season.
Yengi,meanwhile,was influential once again in attack on the back of goals in his two previous games for the Reds,who have surged into second spot on the A-League ladder – one point off Central Coast Mariners.
Sydney struggled to generate any meaningful early chances until just before break,when Bobo had his shot blocked from close-range after getting on the end of a sweeping counter led by Kosta Barbarouses.