While I wouldn't want to make changes as consistency is a key element to a successful side, players who aren't pulling their weight might as well be replaced by someone who might/will.
ENGLAND SERIES AVERAGES
Batting
Strauss : 309 runs @ 61.80
Bell : 53 runs @ 53.00
Collingwood : 221 runs @ 44.20
Flintoff : 171 runs @ 42.75
Pietersen (unavailable) : 153 runs @ 38.25
Prior : 180 runs @ 36.00
Swann : 106 runs @ 35.33
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Cook : 143 runs @ 28.60
Broad : 104 runs @ 26.00
Anderson : 77 runs @ 25.67
Bopara : 104 runs @ 20.80
Bowling
Onions : 8 wkts @ 27.88
Anderson : 12 wkts @ 31.50
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Flintoff : 7 wkts @ 48.57
Swann : 6 wkts @ 57.50
Broad : 6 wkts @ 57.50
Panesar (dropped) : 1 wkt @ 115.00
The following are seriously not carrying their weight enough :
COOK : scored 95 but that's over 2/3 of all his runs and he is averaging a meagre 12.00 from his other four innings (4 inns, 48 runs)
BOPARA : highest score of 35 that was thoroughly unconvincing. How can you give a fourth Test to someone averaging 20.80 and yet to score more than 35!?!?!?!
BROAD : a decent 55 in the last Test, nearly treble his previous highest series score, but batting down at no 8 his wickets have to be the major factor in his selection/retention and six in three Tests is not enough (for a seamer) I'd rather have a wicket or two more a Test than his runs, Swann and Anderson have also scored runs so his runs aren't as key as many seem to make out.
SWANN : only thing in his favour is he is our no 1 spinner at the moment, unless we want to throw someone like Rashid in at the deep end. One thing in his favour over Broad is he took 4/87 in a previous Test to help win it, Broad's 2/38 was his best figures of the series.
BEST BOWLING OF ASHES SERIES (COMBINED
5/80 Anderson (ENG)
5/92 Flintoff (ENG)
4/58 Onions (ENG)
4/87 Swann (ENG)
4/103 Hilfenhaus (AUS)
3/63 Hauritz (AUS)
3/89 Siddle (AUS)
3/87 Johnson (AUS)
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2/38 Broad (ENG)
1/12 Clarke (AUS)
1/38 Collingwood (ENG)
1/115 Panesar (ENG)
So Broad is the only frontline bowler bar Panesar (1 Test) not to have taken 3+ wickets in an innings. Hauritz, Johnson, Siddle, Anderson, Hilfenhaus and Swann are all averaging 18+ with the bat so Broad is not proving leagues ahead on that score either. So he offers no great volume of wickets and no great match-winning threat either - with bat or ball. That 55 was a good knock, but perhaps simply bit into England's bowling time and his contribution was the pick but maybe a 4 or 5 wicket haul would have been more useful towards winning the Test. If anything his 55 delayed us bowling and pushed the game closer towards a draw.
We can't afford to have Swann, Flintoff AND Broad in the bowling attack if they're not going to pose constant threats. Flintoff and Swann have match-winning potential, Broad is at best offering 1-2 wickets and that isn't enough if Flintoff and Swann don't fire as it means we rely too heavily on Anderson and Onions.
So I'd be tempted to drop Bopara, Cook and Broad. Broad for lack of wickets, Cook for lack of contributions (1 in 5) and Bopara for being too weak a no 3 and not looking a Test cricketer against this level of opposition. Maybe give Bopara time AFTER this series, but for now he is simply not scoring enough runs.