Darren Bent and Micah Richards have both returned to their clubs after being ruled out of England's Euro 2012 qualifier with Wales on Tuesday due to injury.
Bent had not been able to train in the build-up to Friday's win over Bulgaria after picking up a groin problem.
And with director of football development Sir Trevor Brooking confirming Sunday morning that Bent did not train yesterday either, coach Fabio Capello decided there was little point keeping the Aston Villa man.
It is thought that Manchester City defender Richards has suffered a hamstring injury.
With Manchester United's Chris Smalling expected to occupy the right-back role at Wembley this week, and Phil Jagielka able to provide cover, Capello opted to let Richards go straight back to his club.
It leaves England with 23 men remaining from Capello's original squad, so there will be no replacements called into the party.
Wales will head into Tuesday's game buoyed by Friday's impressive 2-1 victory over Montenegro - their first points of their Euro 2012 qualification campaign and their first win against a top-20 nation since 2002.
That result left England knowing four points from their final two qualifiers will assure them of a place in next year's finals.
"We won't look too far ahead,'' he said. "They got a nice boost winning against Montenegro.
"We'll try to win the Wales game first. It will be tough but with our home support we should be fine.''
England have gone four games without a home win - their worst run in almost three decades - but Walcott is upbeat about the prospects of that changing.
"We need to take our away form to Wembley," he said. "It will come. The pitch is terrific so there's no real excuses."
He added: "We've got great balance in the squad. Everyone is on their toes - there's so much competition for places.
"The amount of pace we've got going forward - not just in the starting line-up but on the bench too - it's a very, very attacking team.
"That's what we want to be. If we can counter-attack with players we've got we've always got a chance.''
Bolton defender Gary Cahill reflected on his contribution to the win over Bulgaria.
His partnership with John Terry in defence helped England keep a clean sheet and he scored England's first goal in the 3-0 win.
"It was a fantastic night all around,'' he said.
"I thought we defended really well as a team and then I scored so I was really pleased.''
Cahill, who had been linked with Arsenal in the last days of the transfer window, added: "There's a lot of competition for centre-back in the squad. I just wanted to go out and play on the back of what was a difficult week and I was grateful for the opportunity.''
Cahill is encouraged by what has been described as a new generation of talent coming into the England team.
"I've been around the squad a little while and seeing the quality now with the young players coming, there's good blend with the experienced pros which are here,'' he said.
Looking ahead to the game against Wales, who beat England's rivals for the top spot in the group, Montenegro, Cahill added: "It's going to be a difficult game and we'll be trying to get a good result.
"The table's looking healthy - Wales did us a favour the other night."
