The League One side looked on track for a memorable upset when former Fulham player Cauley Woodrow lashed them in front inside four minutes at Adams Park.
King’s goal, flicked in cleverly from a near-post corner to equalise just after half-time, put the visitors into the ascendency with Silva’s team creating more than enough chances to finish the tie in 90 minutes ahead of their upcoming clash with Wolves.
Instead penalties were needed to determine who progressed to the quarter-final, Fulham spurning two chances to win it before Issa Diop struck the winning kick to edge it 5-4.
Silva, whose side were on a four-match losing run in the Premier League, praised King for his 'streetwise' finish from Kevin’s corner to rescue his side - as they prepare to take on Wolves on Saturday.
“He has a role there,” he said. “His role was to go in front of the player. He was streetwise and that’s what I want from all of the players.
“We have a role to try and block players in that situation. He was very smart the way he finished that moment.
“I’m very pleased to have him with us. We, and himself, prepared him very well last season. Since he was 16 I spoke with him, that the season after he is going to be a senior player for this club.
“He made his debut at 17. He’s a lovely boy, he’s very humble. He has many things to improve, his finishing, but he has many good things that it is not easy to find in football at his age.
“He’s playing every game because we trust him and he deserves the trust.”
Fulham looked short of confidence after going a goal down and struggled to break Wycombe down.
“These type of moments can happen in this competition,” he said. “To be honest, I think we did enough. We knew we were stronger than them.
“In these type of moments we have to keep positivity around ourselves, because these type of things happen. First shot on target, goal for Wycombe. That’s football.
“The results haven’t been at all good enough for us. Some difficult circumstances, some difficult opposition. But I think the team is being very competitive in all the games. I’m sure that with all the squad available we are going to be much stronger.”