Simon Cox fired West Brom into the fourth round of the FA Cup with a hat-trick against an under-strength Cardiff side who now have bigger fish to fry.

Goals from Peter Odemwingie and Cox opened up a two-goal lead just after the half-hour, only for a City side showing 10 changes to be level after 50 minutes courtesy of former Albion striker Robert Earnshaw and substitute Joe Mason.

It was Republic of Ireland striker Cox, though, with only one goal this season and that back in August, who had the final say with a 25-yard strike on the hour and a tap in at the death.

It was undoubtedly clear Bluebirds boss Malky Mackay had Tuesday's Carling Cup semi-final first leg clash at Crystal Palace higher on his agenda with seven players were rested.

There appeared to be a hint of good fortune about the Baggies' opener after seven minutes, although the fact referee Lee Probert ignored strong penalty appeals shortly beforehand seemingly evened up the score.

James Morrison produced a surging run to the deadball line, with his cut-back clearly hitting the hand of a sliding Dekel Keinan.

The argument from Probert appeared to be it was one of those Keinan - this week recalled from a loan spell with Palace - was unable to avoid.

Three minutes later, however, and Albion had their opener courtesy of Odemwingie's fifth goal of the season, and his third in his last five appearances.

Goalkeeper Tom Heaton's booted clearance landed at the feet of Craig Dawson in the centre circle, the midfielder delivering a first-time punt back up the field for Odemwingie.

Although he appeared to be a good few yards offside, there was no flag, allowing him to bury an 18-yard effort beyond Heaton.

The visitors then proceeded to dominate possession, albeit without testing goalkeeper Ben Foster and putting the Baggies backline under any undue pressure.