England paceman Stuart Broad is proud of the way his side has restricted Australia captain Michael Clarke in the Ashes series so far but warned they cannot let the star batsman off the hook.
Scores of 10 and three during Australia's eight-wicket defeat by England in the third Test at Edgbaston left Clarke with a meagre series aggregate of 94 runs in six innings at an average of under 19.
Back and hamstring injuries have restricted Clarke to just eight Tests in the past year and, with Australia 2-1 down in the five-match Ashes series, there is a sense the 34-year-old is approaching a crunch point in his brilliant career.
"We obviously do a lot of research on him because he averages something like 52 in over 110 Tests which is remarkable, the career he's had," said Broad speaking Tuesday at his Trent Bridge home ground, where the fourth Test starts on Thursday.
"We've made it hard for Michael. We know how dangerous he is. He is such a key player for them and it's been going well so far."
Thursday's match will see England go into a Test without James Anderson for the first time since both he and Broad were controversially rested from the team that played the West Indies in a rain-affected draw at Edgbaston in 2012.
Anderson, who took an Ashes best six for 47 at Edgbaston last week, has been ruled out with a side strain.
As well as being England's all-time leading bowler in Tests with 413 wickets, the 33-year-old Anderson has a brilliant record at Trent Bridge with 53 wickets in eight Tests at an average of 19.24.
"Jimmy extracts the most out of this wicket as any bowler I have seen and not just swing," said Broad.
