"I told David the other day that I thought he has never been in such good form either mentally or physically and he agreed with me," Capello told a news conference on Friday.
"I can't understand how a player who is playing so well can be left out of any national side."
Beckham was dropped by newly appointed England manager Steve McClaren after stepping down as captain following a disappointing World Cup, but the midfielder has made it clear that he still wants to play for the national side.
He was also discarded by Capello after he announced his decision to leave Real Madrid and sign a five-year deal for MLS side LA Galaxy worth $250 million.
However, Beckham's continued dedication in training persuaded the Italian to backtrack on his pledge that he would never again play for Real Madrid.
The 32-year-old has been one of the most influential figures in Real's late-season revival, winning praise from his team mates and the Spanish media for his performances as the club has overhauled Barca at the top of the table.
McClaren, who will name his squad for the upcoming friendly against Brazil and the Euro 2008 qualifier against Estonia on Saturday, said he has not ruled out a recall for the midfielder.
"I've never said the door is closed on David Beckham," McClaren said earlier this week. "I keep my eye on everybody and I said from day one that David's form would be monitored."
