England captain Dylan Hartley was part of the Northampton side well beaten by Saracens.
It's fair to say he pulled no punches talking to BBC Radio Northampton.
"It's a very grounding and humbling experience. Pre-season was going really well and we've had a bit of a shock today," he said.
"We were too passive in the first half and you can't let a good side like Saracens go 40 points up.
"I've been in this game long enough to know that one game doesn't define you and I'm not going to let this derail our season.
"There were a lot of people writing us off before this tournament and a lot of people's prophecies were confirmed today, but we will stay together, keep our heads down and keep working.
"We lost and we didn't lose in a good manner. We were poor. They seemed to win all the 50-50s and scored points every time they turned the ball over.
"We need to continue to believe in what we're doing and be a lot better than we were today."
A nine-try thumping
Saracens 55-24 Northampton
Getty ImagesCopyright: Getty Images
That was some afternoon for Saracens.
Read all about their crushing win over Northampton Saints.
What a finish that was! Before we leave you today, let's just round up this afternoon's thrilling Premiership action.
Reaction
FT: London Irish 39-29 Harlequins
Getty ImagesCopyright: Getty Images
London Irish captain David Paice told BT Sport:
"The Championship is very physical but the speed of the Premiership is what we struggled with and that probably showed in the last 20-30 minutes.
"But the guys hung in and worked hard for each other."
Post update
Paul Grayson
Former England fly-half on BBC Radio 5 live
What a fantastic victory for London Irish. They haven't been lucky today.
Harlequins may have perhaps underestimated them a little bit but soon got their house in order.
It has been through positive London Irish play. They are well worthy of their win.
Post update
Chris Jones
BBC 5 live rugby union commentator
Look at the reaction from the London Irish bench.
They're celebrating like they have won the league and so are the fans.
Full-time
London Irish 39-29 Harlequins
Phew. What finish. But London Irish hold on for a brilliant win.
Try (Brendan McKibbin, con Bell)
London Irish 39-29 Harlequins
Getty ImagesCopyright: Getty Images
That is game over.
With Quins having to gamble Brendan McKibbin intercepts a pass and has the simple task of going over from close range.
Tommy Bell once again adds the conversion.
Post update
Paul Grayson
Former England fly-half on BBC Radio 5 live
What was looking comfortable for London Irish, they now have a very fretful two minutes.
Harlequins will go all guns blazing.
Try (Charlie Walker con Catrakilis)
London Irish 32-29 Harlequins
Hold on.
Charlie Walker races away after a brilliant pass by Marland Yarde and Quins are in with a shout.
The penalty goes over from Demetri Catrakilis. Two minutes to go.
Penalty
London Irish 32-22 Harlequins
To make matters worse, Irish kick the resulting penalty and the lead is ten points. That should be enough to seal the win.
Sin-bin
London Irish 29-22 Harlequins
Mike Brown is off and Quins will play the last few minutes with 14 men.
Post update
London Irish 29-22 Harlequins
Mike Brown could be in trouble here. The Harlequins full-back seemed to barge Tommy Bell as the Irish full-back makes his way towards the try line.
Post update
Paul Grayson
Former England fly-half on BBC Radio 5 live
Six minutes is quite a long time with ball in hand. A couple of minutes is enough with ball in hand for Harlequins to score another try.
Try (Danny Care)
London Irish 29-22 Harlequins
Rex FeaturesCopyright: Rex Features
Danny Care snipes over from close range for Harlequins.
Care makes full use of some smart running by his team-mates to dart over and just about ground the ball.
But the conversion is missed so it's still; a seven-point game.
Post update
London Irish 29-17 Harlequins
Irish concede another penalty after a battering ram of a run from Jamie Roberts. Quins are really pressing.
Post update
Natasha Hunt
England World Cup winning scrum-half on BBC Radio 5 live
There are bodies scattered all over the pitch now. We said at half-time that the benches are going to be critical in this game and it is proving to be this way.
It looks like it's really starting to take its toll.
Live Reporting
Owen Phillips
All times stated are UK
Get involved
AFPCopyright: AFP 
Getty ImagesCopyright: Getty Images 
Rex FeaturesCopyright: Rex Features 
Getty ImagesCopyright: Getty Images 
Getty ImagesCopyright: Getty Images 
Getty ImagesCopyright: Getty Images 
Rex FeaturesCopyright: Rex Features 
Latest PostThanks for popping by
That's us done and dusted after a real humdinger of an afternoon in the Premiership.
Tries galore - 32 in total - and drama all the way from the three games - and a total of 232 points. If my maths is correct.
And there is more to come on Sunday.
Leicester Tigers against Bath is a great way to round off the first weekend of Premiership action. Please join us tomorrow afternoon.
Have a great evening. Bye.
A flying start for London Irish
London Irish 39-29 Harlequins
The second of two thrilling matches at Twickenham saw London Irish victorious on their return to the top flight.
Here's how they beat Harlequins.
London Irish 39-29 Harlequins
London Irish make a winning return to the Premiership with a thrilling bonus-point victory over Harlequins at Twickenham.
Read moreRobson scores four in Wasps win
Wasps 50-35 Sale
Dan Robson had plenty to smile about this afternoon, running in four tries in Wasps' win over Sale...
Wasps 50-35 Sale
Dan Robson scores four tries as Wasps see off a resilient Sale to open their Premiership season with a bonus-point victory.
Read more'I'm not going to let this derail our season'
Saracens 55-24 Northampton
England captain Dylan Hartley was part of the Northampton side well beaten by Saracens.
It's fair to say he pulled no punches talking to BBC Radio Northampton.
"It's a very grounding and humbling experience. Pre-season was going really well and we've had a bit of a shock today," he said.
"We were too passive in the first half and you can't let a good side like Saracens go 40 points up.
"I've been in this game long enough to know that one game doesn't define you and I'm not going to let this derail our season.
"There were a lot of people writing us off before this tournament and a lot of people's prophecies were confirmed today, but we will stay together, keep our heads down and keep working.
"We lost and we didn't lose in a good manner. We were poor. They seemed to win all the 50-50s and scored points every time they turned the ball over.
"We need to continue to believe in what we're doing and be a lot better than we were today."
A nine-try thumping
Saracens 55-24 Northampton
That was some afternoon for Saracens.
Read all about their crushing win over Northampton Saints.
Saracens 55-24 Northampton
European champions Saracens begin their 2017-18 Premiership campaign in style with a nine-try thrashing of Northampton Saints.
Read morePost update
What a finish that was! Before we leave you today, let's just round up this afternoon's thrilling Premiership action.
Reaction
FT: London Irish 39-29 Harlequins
London Irish captain David Paice told BT Sport:
"The Championship is very physical but the speed of the Premiership is what we struggled with and that probably showed in the last 20-30 minutes.
"But the guys hung in and worked hard for each other."
Post update
Paul Grayson
Former England fly-half on BBC Radio 5 live
What a fantastic victory for London Irish. They haven't been lucky today.
Harlequins may have perhaps underestimated them a little bit but soon got their house in order.
It has been through positive London Irish play. They are well worthy of their win.
Post update
Chris Jones
BBC 5 live rugby union commentator
Look at the reaction from the London Irish bench.
They're celebrating like they have won the league and so are the fans.
Full-time
London Irish 39-29 Harlequins
Phew. What finish. But London Irish hold on for a brilliant win.
Try (Brendan McKibbin, con Bell)
London Irish 39-29 Harlequins
That is game over.
With Quins having to gamble Brendan McKibbin intercepts a pass and has the simple task of going over from close range.
Tommy Bell once again adds the conversion.
Post update
Paul Grayson
Former England fly-half on BBC Radio 5 live
What was looking comfortable for London Irish, they now have a very fretful two minutes.
Harlequins will go all guns blazing.
Try (Charlie Walker con Catrakilis)
London Irish 32-29 Harlequins
Hold on.
Charlie Walker races away after a brilliant pass by Marland Yarde and Quins are in with a shout.
The penalty goes over from Demetri Catrakilis. Two minutes to go.
Penalty
London Irish 32-22 Harlequins
To make matters worse, Irish kick the resulting penalty and the lead is ten points. That should be enough to seal the win.
Sin-bin
London Irish 29-22 Harlequins
Mike Brown is off and Quins will play the last few minutes with 14 men.
Post update
London Irish 29-22 Harlequins
Mike Brown could be in trouble here. The Harlequins full-back seemed to barge Tommy Bell as the Irish full-back makes his way towards the try line.
Post update
Paul Grayson
Former England fly-half on BBC Radio 5 live
Six minutes is quite a long time with ball in hand. A couple of minutes is enough with ball in hand for Harlequins to score another try.
Try (Danny Care)
London Irish 29-22 Harlequins
Danny Care snipes over from close range for Harlequins.
Care makes full use of some smart running by his team-mates to dart over and just about ground the ball.
But the conversion is missed so it's still; a seven-point game.
Post update
London Irish 29-17 Harlequins
Irish concede another penalty after a battering ram of a run from Jamie Roberts. Quins are really pressing.
Post update
Natasha Hunt
England World Cup winning scrum-half on BBC Radio 5 live
There are bodies scattered all over the pitch now. We said at half-time that the benches are going to be critical in this game and it is proving to be this way.
It looks like it's really starting to take its toll.