Leroy Lita bagged a hat-trick as Coca-Cola Championship leaders Reading came back from 2-0 down to knock West Brom out of the FA Cup and deny the Premiership strugglers a fourth round derby with Birmingham.

Lita, 21, had not started a match since the beginning of last month and had only just recovered from an ankle injury but the summer buy from Bristol City was simply sensational as Bryan Robson's side wilted and were finally despatched in extra time.

Albion had made an excellent start thanks to a first half brace from Richard Chaplow, a most unlikely source.

The 20-year-old former Burnley man had never before found the net in a senior fixture but was able to beat Royals goalkeeper Graham Stack twice before half an hour had passed.

Albion had been without almost a whole team of experienced campaigners, out through injury, suspension or international commitments.

Chaplow, striker Robbie Earnshaw, goalkeeper Chris Kirkland and defender Martin Albrechtsen were all restored to the starting line-up, while youngster Jared Hodgkiss was handed a debut at right-back.

But the Royals, who could legitimately claim to have been favourites following the 1-1 draw at the Hawthorns, did not field a full-strength side either as manager Steve Coppell simply chose not to.

Prolific striker Dave Kitson was rested and usual partner Kevin Doyle, who has just signed a contract extension to 2009, was on the bench to allow Lita to play alongside the Royals' less successful Irish import Shane Long.

Lita made his intentions clear by firing an early chance into the side-netting after Steve Sidwell had robbed Junichi Inamoto in midfield but Chaplow responded with a ninth-minute opener, drilling low past Stack after Ronnie Wallwork had opened up the home defence.

Chaplow's second arrived on the half-hour mark and could not have been much simpler; a tap-in from two yards. Nathan Ellington was the man who had made it happen by firing in a first-time effort which Stack found too hot to handle and with no defender anticipating the goalkeeper's parry Chaplow could not miss.

Long was finding his own step up much harder, mis-kicking a good chance in a panic, and he was booked in the 38th minute for a crude challenge on Albrechtsen, the goal hero at Wigan on Sunday.

Reading needed an early comeback and Lita duly provided that within five minutes of the restart with a smart finish to beat Kirkland at his near post after Albrechtsen had been evaded with a nifty turn.

The approach play had been top quality too, with John Oster dancing in from the right to set up his team-mate.

Kirkland had to collect at Lita's feet within seconds of the restart as the home side sensed it might be their night again in a season that has seen them beaten only by Plymouth and Arsenal.

Wallwork had to block in front of a post to stop Long from hitting the target and Sidwell was only just off target from the edge of the area as Reading began to take a grip on the game.

Albion looked nervous and their inability to keep possession made them especially vulnerable as the confidence began to course through the home side's veins.

Even Long had it in abundance now as he produced a cheeky back-heel to begin the move that led to James Harper setting up the equaliser in the 65th minute, with Lita's rising drive from 25 yards perfectly placed as well to give Kirkland no chance.

The Reading fans had been taunting the away contingent since the first Lita strike and suddenly those boasts of superiority had been borne out by action on the pitch.

Albion attacks were rare now but Ellington forced Stack into a save with a rising drive from a tight angle on the right when perhaps a pass would have been the better option.

But Reading were now relentless in coming forward and Albion relieved merely to stay in a tie they must have thought they had wrapped up at the break.

Doyle came on for Long in the 90th minute and Inamoto was replaced by youngster Rob Davies for extra time.

Lita's hat-trick arrived just three minutes after the restart as he fired joyously past Kirkland after last defender Albrechtsen had only half-stopped Harper's burst into the box.

There was still time for the Premiership side to respond but they never came close as the night belonged to Lita and Reading.

Teams

Reading Stack, Murty, Sidwell, Gunnarsson, Lita (Cox 101),

Hunt, Oster (Osano 107), Harper, Ingimarsson, Makin,

Long (Doyle 90).

Subs Not Used: Hahnemann, Little.

Booked: Long, Lita.

Goals: Lita 50, 65, 93.

West Brom Kirkland, Greening (Dyer 81), Chaplow, Albrechtsen,

Carter, Curtis Davies, Ellington, Earnshaw,

Wallwork (Nicholson 106), Hodgkiss, Inamoto (Rob Davies 90).

Subs Not Used: Elvins, Kuszczak.

Booked: Wallwork.

Goals: Chaplow 9, 32.

After Extra Time

Att: 16,737

Ref: P Taylor (Hertfordshire).