Tony Cottee told Sky Sports News that he was surprised to see Rio Ferdinand left out of England's squad for Euro 2012.
The Manchester United defender was omitted from Roy Hodgson's 23-man party for this summer's tournament in Poland and Ukraine, but Chelsea skipper John Terry has been included.
Ferdinand and Terry's relationship has reportedly soured after the latter was charged with racially abusing Rio's brother and QPR defender, Anton, in October of last year.
There was intense speculation that Hodgson would only pick one of the defenders in his squad and Terry, who captained his nation during the 2010 World Cup, has been given the nod for "footballing reasons".
Cottee says he understands that team morale could have suffered if Ferdinand and Terry were both selected, but feels England will now be shorn of one of the "best centre-halves in the country".
"It is a huge shock that Rio is not in the squad," said ex-striker Cottee, who won seven England caps. "I thought that if anyone would be left out it would be John Terry.
"Roy Hodgson has got a lot of explaining to do as this is a guy [Ferdinand] that has played in the Manchester United team, been in good form, and there is nothing wrong with his fitness. If it is a footballing decision I am baffled by it as Ferdinand is one of our four best centre-halves.
"I would have picked Terry, too, but you can only pick them both if there is not an issue between them. However, I don't think we have picked the best squad."
Arsenal tyro Alex-Oxlade Chamberlain has also been rewarded for his bright cameos with the Gunners this term by being named in Hodgson's maiden England squad.
Cottee does not think the former Southampton youngster will propel his way into his country's starting line-up, but says he could be a major weapon coming on as a substitute.
"I think he deserves his place in the squad as he has shown real excitement and real quality when he has come off the bench for Arsenal," added Cottee.
"Arsene Wenger has used him sparingly but I think he is a great player. He is a star of the future; he has a great touch, tremendous pace and is a good finisher.
"If you play [Theo] Walcott and it isn't quite happening, you can bring him on. I think we will see him playing in some of the games but he won't be a starter."