Miyaichi looked set for a baptism of fire as he made his first start for Bolton in the hostile surroundings of The Den in south London, but he quickly silenced the notoriously volatile home supporters with a superb individual goal in the fourth minute on Saturday.
Sam Ricketts lofted a quick free-kick toward Miyaichi and the 19-year-old, who joined Wanderers on loan from Arsenal in January, showed great pace and desire to surge away from Millwall defender Alan Dunne before driving a shot high past goalkeeper Steve Mildenhall.
It was the perfect way for Miyaichi to announce his arrival at Bolton in just his second match for the club and Coyle is confident it won't be the last time he steals the spotlight.
"His second-half performance against Wigan last week was terrific, and from that moment there was no doubt he was going to start today," he said.
"He showed what a talent he is. There's other stuff he can learn, but he's brave and tough - he stood up to some of the treatment he got today - and he always plays with a smile on his face, which I absolutely love."
Miyaichi's goal allowed Bolton to cruise to a straightforward victory, with David Ngog scoring their second goal in the 59th minute, and progress to the last eight came as a welcome respite for Coyle after his side slumped to second bottom of the Premier League last weekend.
Coyle revealed he has been a long-term admirer of Miyaichi and was determined to bring him in on loan from Arsenal, even though the teenager has so far made only two substitute appearances for the Gunners.
"First and foremost I am a football fan and I want to be excited by some of the players I've got in my team, and Ryo Miyaichi certainly does that," he said.
"In football terms he is a baby, a kid. I saw when Arsenal brought him in and then watched him on loan at Feyenoord last year, and he always caught my eye.
"I spoke to Arsene (Wenger) a few times about him and did everything I could to get him to the football club."
After last season's painful FA Cup semi-final defeat against Stoke, Coyle would love to make amends at Wembley this term, but for now he was just relieved to avoid a potential upset against Championship strugglers Millwall.
"I know from both my playing and coaching days how difficult any cup tie can be," he said.
"I've been an underdog many, many times. I think we started well. It probably took Millwall 15 or 20 minutes to get into the game, but when they did they had a few corners and a bit of pressure.
"We stood up to what was always going to be a difficult test. We defended well - Tim Ream had a terrific debut."
Source: AFP
Source: AFP