Davies was making up ground to leaders Davide Giugliano and Tom Sykes in race one before a technical problem forced him off the track at the Rivazza corner.
During race two, Davies was all set for a third-placed finish behind the Kawasakis of Jonathan Rea and Sykes, but he once again saw is race ended early, this time by an oil leak.
"A disastrous day for us obviously," Davies told reporters. "We were in a position to be able to complete two good races here today and instead we go home with nothing. In race 1 a technical problem stopped me and so I hoped to be able to make up for that in race two.
"Once the second race got underway, I knew something was wrong almost right away. I was using the second bike and had to press a couple of buttons to change the setting and after that the bike seemed a bit smoother.
"But then I started to have other issues, my foot came off the footpeg and I realised there was a little oil leaking, so I tried to be careful and hoped it wouldn't get worse but it wasn't possible to finish the race. A day to forget."
As a result of his double DNF, Davies slipped down to fourth on the World Superbike standings and is now 117 points behind leader Rea, who posted a double victory at the Italian circuit.