Ghana U20 coach Sellas Tetteh has defended his decision to start striker Richmond Boakye-Yiadom from the bench in the 3-2 win over Portugal.The Juventus-owned hitman who spent last season on loan in Serie-B with Sassuolo emerged the game changer when he came on as a second half substitute.Boakye-Yiadom played a part in Ghana’s second goal to tie the game at 2-2 before scoring from a free kick to win it for Black Satellites.The victory sees Ghana progress to the last eight as the only surviving African side in the tournament being hosted by Turkey.Some have however raised questions over the bench role of Boakye-Yiadom who has already been capped at senior level for Ghana.But the experienced coach explains the 20-year-old is being managed with a slight injury but hailed the effect of his substitution.“Simply because he missed two training sessions because of a slight injury,” Tettehsaid.“We therefore had to manage the situation and I thought the game at the time of his introduction was what we needed and it worked to perfection.“One thing every coach wants is to make a substitution that works to perfection and I am thankful for that.”Ghana who started the tournament with two defeats will now be facing Chile on Sunday for a place in the last four of the competition