Mark McCall insists Saracens were not good enough against Cardiff Blues, even though they scored six second-half tries and ran out 51-25 winners at Allianz Park.

Ben Earl came off the bench to score two second-half tries while wing Sean Maitland also added two in quick succession, but the former champions had to turn it around after a poor first half.

Blaine Scully and Matthew Morgan both crossed for the Blues to hand them an 18-13 half-time lead and, despite the improved second-half display and ultimately comfortable win, McCall cut a frustrated figure at full-time.

"There's a feeling of dissatisfaction in the dressing room because of how the first half went today. There are certain things we did which just aren't good enough," the director of rugby said.

"It was a strange first half. We had a lot of possession and field position but we weren't very strong with either, and we gave away two very sloppy tries, especially the second.

"We knew we needed an extra five or 10 per cent in a couple of areas and the players were very clear at half-time about what needed to improve.

"We played better in the second half but we still didn't play brilliantly, and we had a few things go our way too.

"Individually there were some positives today but as a team we're not really where I'd want to be. We need to be better next week."

Richard Wigglesworth's try and two Owen Farrell penalties were all Saracens had to show from a first half in which they were outfoxed by the impressive Blues, who played with a high intensity.

Scully crossed out wide for his first try of the season before Morgan's stunning individual effort hinted at an upset.

But Earl's introduction changed the game and he scored twice in quick succession, before Maitland (two), Christian Judge and Ben Spencer ensured Saracens moved back to the top of Pool 3 above Glasgow Warriors.

The Blues sit third and know they need to beat Saracens in the reverse fixture next week to have any hope of reaching the last eight.

"It was an excellent first 40 minutes for us. Saracens are a class outfit and they came out fast so we did really well to claw our way back into the game and lead at half-time," said head coach John Mulvihill.

"Defensively we stood up really well in the first half, and we also moved the ball well. In the second half Saracens took real care of the ball and pinned us down at one end.

"They're really smart kickers. We probably coughed up a bit too much possession and gave them too much field position, but they're a great team and they just got on a roll."