While the exact date of his return from a stomach injury is unknown, his club have made it quite clear via their official Twitter account that he will not be available for England's final two vital World Cup qualifiers in early October:
Theo Walcott will have a minor procedure on his abdomen and has been ruled out until after the international break: http://t.co/xSMy37Jfcc— Arsenal.com (@Arsenal) September 24, 2013
Those games, against Montenegro and Poland, will dictate whether England qualify directly for the finals in Brazil next summer, will need a playoff to reach the tournament or fail to qualify altogether.
Roy Hodgson would have hoped to have had as strong a squad as possible to pick from, but he will now be without the Arsenal man who has been a regular on the right flank.
Hodgson, quite simply, cannot afford to fail to win both of these matches.
With one of his fastest and most direct attacking outlets gone, England's entire attacking plans may indeed have to change. Not noted for their patient, probing buildup play or particular prowess at scything through packed defences, playing through the spaces between centre- and full-backs could be key for England.
Walcott's pace will be a loss, then, though question marks remain over his end product at international level. He would almost certainly have been in the starting lineup had he been fit, though, so Hodgson must find the right alternative who can tip the attacking balance in his side's favour.
Alternatives to Walcott
Andros Townsend was in the last England squad, though as a left-footer he is much likelier to cut inside and narrow the attack than Walcott would have been. As he is an entirely inexperienced player at the top level, it would also be extremely risky to throw him into these telling matches. The same can perhaps be said of Raheem Sterling or Wilfried Zaha.
All three might be better used as impact substitutes if required.
Spurs' Aaron Lennon would be a natural replacement but has been injured and is only expected to recover by early October, per PhysioRoom.com, giving him minimal time to regain full fitness before the qualifiers.
Hodgson perhaps has two alternative options.
Perennial substitute James Milner is seen as a "safe and reliable" option, so Hodgson may opt to start him from the right side, offering protection to the defence on that flank and plenty of energy, if not terrific mobility and creativity, when going forward.
A switch later in the game to utilise one of the more dynamic wide men could give England late impetus if needed.
The other possibility might be altogether more attractive: play Danny Welbeck from the right side.
The Manchester United forward, who has been in excellent form for his country and seems something of a favourite of Hodgson's, will expect to be involved.
Moving Welbeck to the right side allows his athleticism, pace and versatility to be utilised to England's advantage, as he will work diligently to control the oppositions' attacks down that side while also being instinctive enough to get forward and make up an extra central threat when the opportunity arises.
England can still opt to bring on one of the more natural wide attackers if the need arises, shifting Welbeck centrally or removing him as needed, while Milner—almost a certainty to be in the squad despite his fleeting appearances at club level—would be the more defensive-minded change if needed.
Starting Welbeck in place of Walcott on the right gives England a replacement with good pace and attacking mentality and keeps a regular starter in the side.
Perhaps best of all, it will allow Hodgson to go with the country's two best attackers, based on both form and ability, in the team for the two most important international games of his England career thus far.