The England manager had said Terry will miss Saturday's match against the world champions for purely football reasons, insisting it has nothing to do with allegations of racism that have been made against his skipper.
Capello wants to 'check other players' and has described the impressive Jagielka as 'the driver' of his back four when Terry has been absent in the past.
Back in contention: John Terry could yet start against Spain at Wembley
But on a day Spain named a squad packed with many of the world's finest players, Capello discovered the Everton defender is struggling with a toe injury and is expected to be sent back to Merseyside after reporting for international duty.
If the boss insists on leaving out Terry until next Tuesday's friendly against Sweden, England would probably face David Villa and Fernando Torres with the untried partnership of Gary Cahill and Joleon Lescott.
Setback: Everton defender Phil Jagielka (right) is suffering with a toe problem
Phil Jones is an alternative, but Capello is considering using the Manchester United player in central midfield.
Further setbacks would put pressure on a team severely weakened by the decision to leave out Wayne Rooney and the absence of other key players such as Steven Gerrard, Jack Wilshere, Ashley Young and Rio Ferdinand.
Adrian Bevington, managing director of Club England, insisted that Capello's intention to leave Terry out against Spain was not a direction from the FA.
Experiment: Phil Jones (right) could be set for a midfield role on Saturday
Sportsmail understands Anton Ferdinand is due to meet police on Tuesday, although it is unclear if the discussions would concern the death threat that was sent to Queens Park Rangers or the original allegation that Terry shouted racist abuse at Ferdinand during Chelsea's defeat at Loftus Road.
Backing: Capello has selected Terry for the friendlies despite the race row
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Source: Daily Mail
Source: Daily Mail