Davies in the swing on his return to Riverside

Wicketless in his first six overs, he suddenly produced a sensational spell of six for nine in 41 balls and finished with a career-best six for 32 against Worcestershire.

The visitors were dismissed for 171, to which Durham replied with 139 for two, with Paul Collingwood unbeaten on 88, his highest championship score since making 99 at Cardiff early in the 2002 season.

While Davies will have earned a few jottings in the chairman of selectors' notebook, former Durham skipper David Graveney was at the ground principally to see Steve Harmison and Collingwood.

Harmison bowled with good rhythm and took the last three wickets, but it was Collingwood who did himself most favours in his bid to earn selection for the two Tests against Sri Lanka.

Going in after the early exit of skipper Mike Hussey for two, the vice-captain quickly latched on to every opportunity to pull anything short and hit 12 fours. It was only towards the close of another uninterrupted day that he looked in any difficulty.

It was on July 22 last year that Davies broke down with a side strain on the second day of the defeat by Derbyshire at Riverside, having taken his previous best of six for 44 on the first day.

After making his comeback in Perth in January, he roared back yesterday, taking the first six wickets to obliterate the visitors' firm foundations.

They survived Davies' first six overs when he came on first change but then slumped from 75 without loss to 120 for six.

"The wicket suited me down to the ground," he said. "The ball moved both ways off the seam and it probably did more at my end.

"It's important for me to prove last season was not a one-off, but my main aim is to get through a full season. I have worked hard on my core strength to prevent the injury recurring.

"I thought I had an lbw in my first over today and it was beginning to feel as though it wasn't our day until we got the first wicket."

Worcestershire chose to bat when play began on time and despite the fact there was obviously something in the pitch for the bowlers it began to look a good decision as openers Steve Peters and Stephen Moore saw off Harmison and Liam Plunkett.

Harmison found encouraging bounce and got past the bat three times in his first over but remained out of luck, while Plunkett struggled to recpature last week's form as he bowled into the numbingly cold east wind.

Durham were unchanged after their massive win at Leicester, leaving out Victoria's Mick Lewis, and if he thought his best chance of a four-day game was to oust Davies he was quickly disillusioned.

Davies looked threatening in his first over and the absence of a wicket was becoming a real mystery by the time he struck.

It was a beauty which left Peters off the pitch to hit off stump and in his next over he removed the South Africa-born Moore, whose superb on-driving had been the feature of his 46.

Like his opening partner, he was pushing forward to a good-length ball which did just enough to beat the bat and strike his back leg.

Plunkett switched ends with little sign of improvement, although he did beat Graeme Hick twice in an over.

There was a case for giving Harmison another couple of overs before Hick settled, but Mike Hussey turned instead to Collingwood and Hick took ten off his opening over.

That included a streaky four wide of the slips, but Hick began to look more settled and at 106 for two Worcestershire had no cause for alarm.

But Davies then took a wicket in each of his next four overs, starting when Ben Smith padded up to one which nipped back and had him lbw.

Skipper Vikram Solanki was off the mark with a risky single but without addition he pushed forward and edged low to third slip's left, where Gareth Breese held an excellent catch.

The arrival of Gareth Batty suggested a lack of depth in the batting and after edging a four he fell lbw, bringing in James Pipe.

With Steve Rhodes becoming assistant coach, Worcestershire have swapped one Bradford-born wicketkeeper for another but there was little sign of Yorkshire grit as Pipe drove at Davies and edged to Hussey at second slip.

At 120 for six with newly-arrived Sri Lankan Chaminda Vaas shivering at the other end, Hick seemed to decide to go looking for runs. He was aiming to drive Collingwood towards mid-wicket when a slight leading edge saw the ball lob up to mid-on, where Harmison took a good tumbling catch.

After a couple of lusty blows from Australian British passport holder Matt Mason, Harmison returned to take the last three wickets.

He started with two bouncers to Mason then had him lbw with a full-length slower ball before Vaas slashed at a wide one and edged to Collingwood at first slip.

Following his 253 at Grace Road, Hussey made only two before getting an inside edge into his stumps in Vaas's fourth over.

But Collingwood and Jon Lewis then put on 103 before Lewis sliced a drive to gully to fall for 37, and Gordon Muchall dug in for the last half hour to reach 11 not out.

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