Aki grabbed the all-important second-half try that saw his side pull away from the welsh side, who now sit tenth in the GUINNESS PRO12 standings after ending up third last term.
And Reed insists the Ospreys will have to do some soul searching this week ahead of a must-win game at champions Glasgow Warriors next Sunday.
"We're hugely disappointed," he told the South Wales Evening Post. "That display was borderline unacceptable and we've told the players that after the game.
"They have to realise they are accountable. There were schoolboy errors on the pitch but as coaches we are also accountable to drive standards.
"It's a low point in terms of the result but also the endeavour and application in the performance.
"There were a huge amount of individual mistakes, but we also lacked shape and went off-task with a lot of things. In the first three games we were outmanned but that wasn't the case today. We were out-thought and out-fought.
"There was naivety about our back play - we didn't respect the opposition or the ball and tried to force things. We have a lot to work through this week before going to the champions Glasgow next week."
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