O’Brien signed for the Shakers during the summer of 2014 from National League North side Chorley
The now 23-year-old former Manchester United youth defender, who is a 6`5” centre-back, was the Magpies' young player of the year for 2013/14 and signed an initial two-year deal.
O'Brien had spells at Northwich Victoria, Mossley AFC and Radcliffe Borough before joining the Magpies In December 2012 for an undisclosed fee.
He was also named in the divisional team of the year as Chorley won the Evo-Stik Northern Premier League Premier Division.
Injury hampered his progress last season, making just one appearance in an FA Cup tie, but he has shown a keenness to cast aside injury woes and now looks to claim more appearances after his spell at The Shay.