Jon Taylor grabbed a late winner to spoil Gary Johnson's first game in charge of Northampton as Shrewsbury twice came from behind to maintain their promotion bid with a 3-2 victory.
Johnson, who took over from Ian Sampson on Friday, saw his new side get off to the perfect start when Michael Jacobs gave them a sixth minute lead with a 20-yard screamer that flew into the net via the crossbar past a stranded Ben Smith.
But Shrewsbury were back on level terms within two minutes when a cross was not dealt with and David Davies pounced to score from eight yards.
Josh Walker went close with a 30-yard free-kick which Smith tipped over before Cobblers regained the lead two minutes after the restart.
It was Jacobs again who grabbed his seventh goal of the season, cutting in from the left to curl a great shot into the top corner.
But once again, Northampton failed to hold on to their advantage and James Collins was allowed time and space to beat Chris Dunn from the edge of the box in the 51st minute.
Northampton went close with Shaun Harrad firing into the side netting, Jacobs shooting just wide and Walker also off target before Taylor popped up in the 87th minute to fire home with a half volley after a corner was only partially cleared.
That saw Northampton slip to their second 3-2 defeat in five days and they have now gone eight games without a win.
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