Leinster head coach Leo Cullen had mixed feelings about his side's seven-try performance despite a comprehensive 50-21 bonus point victory over Northampton in the Heineken Cup.

Following last week's emphatic 43-16 triumph in Franklin's Gardens, the unbeaten Irish province did the double over Saints with a Garry Ringrose hat-trick and further tries from Tadhg Furlong, Dave Kearney, James Lowe and Caelan Doris.

He happy to make history as the first team to qualify for after just four rounds but there were some aspects of the performance that left Cullen a little frustrated.

He said: "It was a little bit mixed I thought today. People are talking in quite positive terms about the performance, but there's bits in there where we could get ourselves in trouble if we deliver that again.

"On the flip side, it's a win. It keeps us trucking along. We turn our attention to other matters, back to the Guinness PRO14. We had some chances today where we didn't quite capitalise. Defensively, it's never great conceding three tries. There's bits to do there."

In the absence of knee injury victim Jonathan Sexton, Ross Byrne started at fly-half and contributed 11 points before a dead leg forced him off, allowing Skerries youngster Ciaran Frawley to come on for his European debut.

Cullen was impressed with the way Frawley handled himself in front of a 42,041-strong crowd, adding: "Ross, just a dead leg for him. It was great experience for Ciaran Frawley to come on in that game. It's a massive step up. He's 22 years of age. Another positive step in his progression.

Ciaran Frawley was introduced at out-half for the injured Ross Byrne

"You're playing here in the Aviva. We talked about it here yesterday. To get over 40,000 to a regular-season game is brilliant. Hopefully we have a couple of big attendances during this Christmas period as well with the interprovincial games."

For Northampton director of rugby Chris Boyd the biggest disappointment was their failure to come away with a bonus point of any description.

Although Dan Biggar, Ollie Sleightholme and Ahsee Tuala all crossed the whitewash, a fourth try never happened.

Boyd believes a strong finish to Pool One could keep the Gallagher Premiership outfit in the frame for a European knockout spot. They lie second on nine points, a full 10 behind Leinster.

"Certainly the plan coming here today was to secure a bonus point," admitted Boyd.

"We didn't think that winning or losing the game would affect our chances of getting out of the pool or not. I think there's a couple of obvious pools where there's going to be two teams coming out.

"Then there's probably a couple of pools where the runner-up has got a chance. If we can do well against Benetton at home and in the last game at Lyon, then I think we're still alive."