The Reading midfielder, who has netted three goals in three games so far this season, was introduced shortly after the break by boss David Platt.
Jermaine Pennant's sixty-first minute dismissal proved costly as England were forced to revert to a midfield three. Consequently, Sidwell was unable to stamp his authority on the game.
That said the flame-haired midfielder, dubbed the 'new Paul Scholes' by some, hardly put a foot wrong on the few occasions that the ball came his way. Sven Goran Eriksson was at Upton Park to watch the game and will surely be keen to keep tabs on young Sidwell, who knows a future call-up to the full squad is not an impossibility, but mightily unlikely.
Goran Ljubojevic opened the scoring for the visitors in the twelfth minute. Evading the attentions of Paul Konchesky, the midfielder planted the ball firmly past Matt Murray in the England goal.
Incidentally, Murray has now conceded eight goals in two games having let in five as Wolves made their Premiership bow at Blackburn on Saturday.
The English went onto dominate much of the first half, despite occasional dangerous attacks from the Croatians. Jermain Defoe thought he had leveled the game five minutes before the break but his cool chipped finish was ruled out for offside.
Ljubojevic made it two shortly after half time, turning the ball home from close range. Suddenly the game was beyond England. With Sidwell's introduction came Pennant's moment of madness.
In the last minute left-back Pranjic rounded off the scoring with a cool first touch lob over Matt Murray.
England were humiliated by the Croatians but Sidwell can come out of the game knowing that he has done no wrong.