The former international feels a centre-back partnership of the ex-captain and Chelsea team-mate Gary Cahill is key, before hailing Lionel Messi over Cristiano RonaldoJohn Terry damages England's chances at the World Cup.
The Chelsea captain quit the national side following a fall-out with the Football Association in 2012 after being found guilty of racist abuse, but has formed impressively under Jose Mourinho this season.
|5/4||England are 5/4 with bet365 to not qualify from Group D|
"I don't think there's any doubt that the best partner for [Gary] Cahill would have been John Terry ... but John Terry wasn't called in," the former striker wrote in his blog, Blahzil.
"The back up in that particular area is either [Chris] Smalling or [Phil] Jones, now both of those players of course have struggled this season at Manchester United.
"So you've not really got that much consistency in that position - it's the one area of the team which is a concern."
Linker, though, is confident Roy Hodgson's defence will be improved by the return to form of Joe Hart.
He added: "Thankfully Joe Hart has bounced back to form with Manchester City and he'll be hugely encouraged by the fact that he went on to win the [Premier League] title.
"So that's massively encouraging because goalkeepers are an integral part of any defence."
Looking at the World Cup as a whole, the former Barcelona man has pinpointed Lionel Messi as the key attraction over the likes of Cristiano Ronaldo.
"For me Messi is a gift from the footballing gods," he wrote.
"He's just such a phenomenal talent, a player that doesn't only best people but memorises them and produces magical moments, scores a multitude of goals and he's always an honest player.
"He gets kicked, he gets hacked, he gets up. He never dives, he doesn't cheat. He's just a brilliant example for footballers everywhere.
"For me Messi just edges it in the sense that he's more of a team player. I think Ronaldo is a phenomenal talent – brilliant player – love him to bits. But he does play for himself a little bit.
"Messi always makes the right decisions, whether to pass or whether just to finish. The man's a little genius."