Capello was pleased with the performances of Jack Rodwell, Phil Jones and Danny Welbeck as he experimented with his line-up in the shock 1-0 win over Spain.
Now Capello will make eight more changes for Tuesday night's encounter with Sweden - also at Wembley - with Tottenham full-back Kyle Walker pencilled in to start for the first time.
It is likely to leave the Italian with a bigger headache than for the 2010 World Cup in deciding his final 23 for Poland and Ukraine, with the young guns vying with more experienced players for a spot.
Capello said: "It is really important for me to know the value of some players from how they played against Spain and now Sweden.
"I am really happy because this experiment was positive (against Spain). The players who played, Rodwell, Jones, Welbeck, did really well. For these players it was a really important experience.
"I personally checked these players and I am really happy with the performance and the personality and the confidence they showed.
"It is difficult for young players to play with the confidence that they showed with Spain.
"If these players during the season will (continue to) improve, all these players will be ready to play with us with at the Euros."
Capello feels he can quickly weigh up whether a player is of the quality to step up onto the international stage.
He said: "The games are good to improve experience, but the quality of a player you can see in a really short time.
"When you play at Wembley, you can understand the value of a player.
"Jack Wilshere played at Wembley without a problem, Jack Rodwell played 20 minutes with no problem, Danny Welbeck the same. Tomorrow we can see Kyle Walker."
Asked if it will be a tough job to decide his squad for next summer, Capello said: "I hope that I've got problems when it comes to choosing the players.
"I hope all the players here are fit and also the seniors will be fit. But I think next summer we can see a really good team."
Midfielder Parker produced another impressive display against Spain and won the official man of the match award.
But Capello has no regrets about not selecting him for the 2010 World Cup because he was satisfied with the performance of his midfielders during qualifying.
He added: "It is easy the day after (in hindsight). He has improved a lot but the players I took to South Africa had played well for me.
"The qualification campaign for South Africa was fantastic and the midfield was always in my mind for the squad.
"But now Parker is doing good. I monitored him for a long time. Now Parker has improved, he is always in the first XI.
"He is a really good player. I think now he is playing with a really important team like Tottenham and he has improved."
Skipper John Terry, Gary Cahill, Bobby Zamora and Rodwell were also confirmed as starters against the Swedes by Capello.
Capello knows the difficulty of stifling the threat of Sweden striker Zlatan Ibrahimovic, who produced some of the best form of his career playing under the Italian for Juventus.
"Ibrahimovic is a fantastic player," Capello added. "He has good imagination, technically he is fantastic and scores goals from long and short distance.
"He is one of the best players I trained in my life, in my career, and he proved it a lot when at Juventus."