The Pittodrie outfit currently sit top of the Clydesdale Bank Premier League's bottom six and can take a step towards confirming seventh place by beating St Mirren in Paisley tomorrow.
But Osbourne admits there is disappointment that Aberdeen did not make more of the talents at their disposal.
Niall McGinn has struck 20 league goals this season while the 14 goals conceded at home hints at a staunch defence that is matched only by SPL champions Celtic.
However, former boss Craig Brown stepped down and was replaced by Derek McInnes after the side failed to sneak into the top six, conceding a last-minute winner to Dundee United's Rory Boulding in their final game before the split.
Osbourne said: "It feels like the one that got away. Considering the squad we have got it's been a disappointing season.
"But then looking back on last season when we finished ninth, it's been a progression. I suppose we just need to hope we can build on that for next season."