The Qatari champions netted a stoppage-time winner against Sepahan after two substitutes combined and their assistant coach was delighted with their impact off the bench
The Qatari champions had lost 2-1 to Sepahan in the last matchday after Bruno Correa's last-gasp strike but inflicted revenge with their late victory on matchday four.
The game had been heading for a goalless draw before the two substitutes combined, with the Ivory Coast striker getting the decisive goal.
Lang said: "We play as a team and having a strong bench is important especially when you get to 'magic time' so we're lucky to have a good bench."
The result moves Lekhwiya up to six points in Group C, one shy of leading pair Al Ahli and Sepahan with two games to play.
"We won today against a strong team because Sepahan have more experience than us," Lang added.
"This is our first season in the AFC Champions League so six points is good for us and we will try to continue to progress towards the second round."
Sepahan coach Zlatjko Kranjcar wasn't too downbeat despite his side conceding the late goal.
"This is football and anything can happen," he said. "It was a disappointing finish but we still have a chance to go to the second round if we do well in our remaining matches."