Interim Chelsea manager Guus Hiddink praised midfielder Ruben Loftus-Cheek after the teenager came off the bench to score his side's second goal in the 2-0 FA Cup win over Scunthorpe.
Loftus-Cheek swept home after coming on at half-time, adding to Diego Costa's first-half goal as the Blues cruised past their League One opponents.
And Hiddink said: "We have these youngsters and I know them now after three to four weeks.
"I know their abilities, and when it's a possibility, an option, I don't hesitate to bring them in.
"It was a lovely clean finish. He waits, he waits, he waits and he comes in at the right moment.
"He can be of big value now. He's 19... I thought he was 22, 23 when I came in.
"He's a proper grown player already but he's 19 -- we have to be careful on the one hand and on the other I said: 'Hey guys, get it done' and we didn't hesitate.
"We're in a difficult situation to finish in fourth place in the Premier League, so I say OK, give them [the younger players] a try.'"
He said it was "realistically" difficult for the defending champions to reach the top four and added: "You see, the league is so, so strong. All the clubs can go for fourth position."