"I have the summer to think about my selections," he said.
"I can't decide on the team because I don't know which players will be fit."
About the captaincy, Capello said he has narrowed the shortlist down to two candidates.
"I have some idea of who it will be," added the Italian.
"The captain for the Czech Republic friendly in August will be the captain for the qualifiers."
Beckham may be one of those candidates for the captaincy after taking the armband for the friendly in Port of Spain.
The 33-year-old won his 102nd cap for his country against Trinidad and Tobago and said he was "surprised" after hearing he would skipper the side again having stepped down from the role following the 2006 World Cup.
The LA Galaxy player was on the pitch for the first-half before Capello made a handful of changes after the break.
"I was surprised and didn't expect it," Beckham told BBC Sport.
"But I'll always answer the call and be available for my country and captain them as well - it was a surprise but I am honoured to do so."
Despite the end-of-season friendly tag, the former Manchester United midfielder said his England team-mates were told to put in a "good performance".
The lads have had long seasons but they're all here and we've enjoyed every minute of it
"It was a tough performance and the manager was telling us before the game that even though it was a friendly we had to take it seriously," he added.
"It was the centenary game for them but they wanted to beat England and we had to put in a good performance and I think we did that.
"The players in the camp are motivated and whether we have got experienced players or young players we have to play as one.
"The respect is there for Capello and there for one another and that is how it needs to be and the qualifiers are the big thing for us now."
Gareth Barry scored England's opener and his first for the national team with a crisp volley before Jermain Defoe scored his fourth and fifth international goals.
The Portsmouth forward said he was eager to continue "learning" under the stewardship of Capello.
"I enjoyed it. It was important to get the win and I'm delighted to get two goals," he revealed.
"To play for your country is the best thing in the world. The lads have had long seasons but they're all here and we've enjoyed every minute of it.
"I just want to keep learning. When a new manager comes in everyone starts on the same level and to get two goals, I'm delighted."
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