Josh Magennis hit a second half hat-trick as Championship Bolton came from a goal down at half-time to beat League One Walsall 5-2 and reach the fourth round of the FA Cup.

Magennis, who had not scored since September 15, netted three times in 26 minutes to ease the pressure on Trotters chief Phil Parkinson.

Clayton Donaldson and a Jon Guthrie own goal completed Bolton's scoring after Andy Cook headed Dean Keates' underdogs in front after 19 minutes.

So what turned out to be a potentially nightmare afternoon for Wanderers ended on a high note.

Manager Parkinson's selection hand for a tricky tie was weakened by the unavailability of three players – Christian Doidge, Gary O'Neil and Remi Matthews.

A registration wrangle ensured the absence of the trio with goalkeeper Matthews returning to parent club Norwich.

Their League One rivals handed a debut to winger Matt Jarvis, who joined on loan from the Canaries on Tuesday.

It was Jarvis who claimed the assist for Cook to give Walsall a deserved advantage after 19 minutes.

Walsall had already been the better side prior to going in front. From the game's first corner skipper George Dobson curled the ball on to the top of Ben Alnwick's crossbar with the keeper beaten.

Comfortable in possession, the visitors hit the front as Jarvis centred from the Bolton right and Cook rose above his marker to head his 12th of the season from seven yards.

When Bolton did threaten the opposition goal Yanic Wildschut dragged a right foot effort wide while Luke Murphy, restored to the side for the first time since last August, headed directly at Liam Roberts.

Parkinson's response to Wanderers' dreadful opening 45 minutes showing was to take off Wildschut and Josh Vela for Will Buckley and Donaldson.

Parkinson admitted his interval change at Hull on New Year's Day contributed to his team's eventual 6-0 defeat.

And the switch did not pay instant dividends as Donaldson joined team mate Josh Magennis in referee Darren England's notebook.

But within the blink of an eye Bolton turned the interval boos to cheers from a paltry attendance of 5,506 boosted by nearly 1,500 from the West Midlands.

Buckley had a goal disallowed for handball after 54 minutes but Donaldson, who missed a sitter at Hull, was on target three minutes later for the first time since his move from Sheffield United last summer.

Craig Noone made the chance with a twisting run on the byline before veteran Donaldson fired home from seven yards.

Magennis tapped in his first after 60 minutes after Liam Roberts saved an initial attempt.

When Donaldson failed to connect with Noone's left wing cross the ball ricocheted off Guthrie's boot into the net after 63 minutes.

Walsall continued to fight and scored a fortuitous goal of their own. Dobson's shot from the edge of the area took two deflections before the ball bobbled into Alnwick's net off Bolton's Mark Beevers.

However, any home nerves evaporated when Magennis headed home another Noone centre after 80 minutes.

Buckley and Cook hit the post for the respective teams before Magennis finished off his hat-trick show, netting a right foot rebound after his first left-foot effort came back off the post.