The England coach said last year that only 35 players were in contention for the 22 spots in his World Cup squad and with at least 15 almost certain to go, there was little room for late runners or those with question marks over their fitness.
Whether or not King was included in that 35 only the Italian knows, but having watched his unflappable performances against Arsenal and Manchester United recently he could not have failed to be impressed.
With two sound knees King would be a certainty for a seat on the plane to South Africa and many would even start him alongside John Terry or Rio Ferdinand in the heart of defence but the fact is that for six days after a match King cannot train.
The 29-year-old's career has been blighted by the degenerative injury, so much so that he has won just 19 England caps and is rarely seen in a Tottenham shirt these days.
When he does appear, however, he oozes class.
In Tottenham's 2-1 home win against Arsenal, only his 17th appearance of the season, he was calmness personified, snuffing out attacks and using the ball simply and effectively in the hurly burly of a north London derby.
Despite a 3-1 defeat at Manchester United on Saturday he again looked the best defender on the pitch, eclipsing highly regarded team mate Michael Dawson, and even made an impact at the other end with a headed equaliser.
FINAL DECISION
Provided the pain in his knee subsides King could feature in two of Tottenham's last three matches as they push for a Champions League place, giving him further chances to impress Capello as he nears his final decision.
"With doubts over Rio Ferdinand's fitness, it would be placing your fate in the lap of the gods to take a player with such injury problems, but, against my better judgment, I would put him on the plane, simply because he is streets ahead of the alternatives," Liverpool's former centre-back Alan Hansen told the Daily Telegraph on Monday.
An injury to Terry or Ferdinand, a player with a history of back trouble, would leave England short at the back especially with West Ham United's Matthew Upson, a regular in Capello's squad, looking short of international pedigree.
"Taking King, a player who could have been a regular were it not for his injury problems, as cover is a risk, but it is one worth taking," Hansen added.
While the central defensive area continues to cause alarm, at least the return of left back Ashley Cole to Chelsea's title push and the form of midfielders Frank Lampard and Steven Gerrard will be reassuring for Capello.
Lampard has hit nine goals in his last seven games while Gerrard appeared back to his best when scoring in Liverpool's 4-0 thrashing of Burnley on Sunday.
In the wide areas Capello's problems also appear to be easing with King's team mate Aaron Lennon back in action on Tottenham's right.
Before a groin injury halted his season in December, Lennon had jumped ahead of Theo Walcott and Shaun Wright-Phillips and his return could be bad news for the latt
