However, Turnbull and co don't have to wait long to set the record straight as this Friday sees Cardiff take on Bristol in Europe.
And the utility forward is eager for his side to learn from the defeat as they bid to get back to the form they showed earlier in the season.
"We started well, especially with the driving line-out for the try," Turnbull said. "We were down to 14 men soon after that, and we were on the back foot from then onwards, and the Ospreys scored a few tries during that period.
"Every derby you find the opposition picks up their game, no matter who the opponents are.
"We have Monday to look back at where we went wrong against Ospreys and then we'll start the work on the training ground, ready for Bristol in Europe next weekend.
"We'll be looking at what we've done well in the previous matches and develop that back into our game before the test we face on Friday.
"I think we have a good chance in Europe. There are going to be some great games against all three teams, but we have to assess ourselves on Monday to make sure we get back to winning ways at Bristol."
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