The 28-year-old centre-back, who moved to the Reebok from Portsmouth in a £1.5million transfer last August, topped our readers' Player of the Year poll, beating Kevin Davies into runners-up spot with Whites' skipper, Kevin Nolan, in third place.
The experienced and respected defender turned in consistently high performances to become a permanent fixture in the battle to avoid relegation and was highly influential in the decisive final phase of the season when Wanderers were unbeaten in five games and conceded only two goals to escape the threat of relegation.
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Gary Cahill, who arrived from Aston Villa in January and forged an impressive partnership with O'Brien, said the former Bradford City and Newcastle United centre-back epitomised the consistency he is looking for in his own developing career.
"I can only speak for the time I have been here, but Andy has been one of the better players in the team," Cahill said.
"I always base my performances on trying to play consistently well over a period of time and that is what he does.
"He's set a level and he sticks to that, week in, week out, and he's been terrific for the team."
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