In the wash-up from the first Test at Cardiff, talk is surrounding the team changes for the second Ashes clash on Thursday at Lord's.

Steve Harmison is in strong contention for an England recall after the in-form paceman claimed another bag of wickets for Durham, ripping through Yorkshire with five for 60. 

Meanwhile at Cardiff, Australia's Ashes debutant Peter Siddle provided a gut-busting and menacing final-day performance on the slow, flat Sophia Gardens pitch.

The Lord's Test could well be a showdown of the two paceman.

Harmison is seen as England’s answer to unsettling the Australian batting attack. He has already unnerved young Australian opener Phillip Hughes in the tour game at Worcester, upsetting the small left-hander by getting the ball to explode off a good length.

Back in the first session at Lord's in 2005, Harmy struck Justin Langer, Matthew Hayden and Ricky Ponting, on the elbow, head and face respectively.

Siddle demonstrated his instincts in the first innings at Cardiff, squaring up Ravi Bopara with a rising delivery which hit the England No.3 under his helmet.

The former wood chopper was aggressive and verbal to the English batsmen, as he toiled hard throughout his spells.

In the second innings, Siddle battered England's Graeme Swann black and blue in one brutal spell, with one over just before tea taking 10 minutes as the No.9 required two visits from the team physiotherapist.

Australian captain Ricky Ponting, impressed by what his saw, bayed for blood by indicating his chest and making a flinching gesture to signify where he wanted Siddle to deliver the ball.

Siddle followed orders and soon after a ball bounced off Swann's helmet.

Ponting later praised Siddle, whose figures of one for 51 off 18 overs did not do him justice. "I love everything about Peter Siddle for that exact reason; the things he did today," Ponting said.

Meanwhile, there are still question marks over Harmison's fitness and his temperament, with Australian coach Tim Nielsen querying the bowler's capacity to maintain his intensity right through a Test match.

Also of importance is the pressure Harmison will be under, especially with the evident demise of Andrew Flintoff.

Flintoff was down on pace and could only muster half-hour spells at Cardiff, a long way from the strength of his 2005 Ashes performances, as he went on to be hit for more than 100 runs in the first innings. 

Freddie also sustained a knee injury whilst fielding, compiling further pressure not only on Harmison, but the much-hyped James Anderson and Stuart Broad.

The Lord's pitch is expected to be of assistance to the fast bowlers of both teams. Harmison may be able to extract unnerving bounce, even off a good length, but Siddle's ability to maintain intensity over long periods may be what will prove to be the main part of Australia's attempt to win the second Test.