Mercedes technical director Paddy Lowe conceded the team were caught out by the weather conditions as Lewis Hamilton crashed out of second practice for the Canadian Grand Prix.
The world champion, as well as team-mate Nico Rosberg, returned to the track at the Gilles Villeneuve Circuit despite rain starting to fall during the session.
The duo were sent out on intermediate tyres but Hamilton aquaplaned off at the turn 10 hairpin and could do nothing as he continued straight into the wall at fairly low speed.
The reigning world champion still did enough to set the fastest time of the session before the incident – which brought out the red flag – and, once the stricken Mercedes was moved, the rain was falling harder and no cars ran in the closing 30 minutes.
Lowe explained that the team were hoping to gather much-needed data ahead of the weekend but the deluge caught them unaware – and also said the rear-end of Hamilton’s car had been damaged as it was recovered.
“It didn’t quite end the way we wanted it to,” he said of the second session.
“The simple reason we went out was to do some practice race starts, that is a normal part of our program. Because the program was very condensed in the short window of time we had, we chose not to do those practice starts in the dry period but go out before it became very, very wet indeed.
“Unfortunately the conditions worsened quicker than we anticipated and the conditions caught Lewis out in an unfortunate manner but we will sort it out tomorrow and we will be fine.
“We were worried watching (the recovery), I think there is some minor damage to the rear-end following the crane handling but nothing serious.”
An unflustered Hamilton explained the incident after the session: “I wasn’t driving very fast,” he said.
“I came into Turn 10 and it was just like ice. It literally was like being on ice and I was just a passenger. It’s not the greatest but you have to laugh it off and the guys will work hard to fix it.”
Hamilton had also topped the timesheet in the dry first practice session following a spin in the same corner – beating Rosberg into second place by more than four-tenths of a second.
The 30-year-old Briton is looking to put the pain of letting victory slip from his grasp a fortnight ago in Monaco by winning for the fourth time in Montreal.
Having dominated the whole of the weekend, Hamilton came into the pit from the lead following the deployment of a late safety car whilst Rosberg and the Ferrari of Sebastian Vettel stayed out.
It proved to be the wrong decision as the two Germans kept Hamilton at bay – with questions still remaining on whose call it was to bring Hamilton in.
“There was a mistake made,” he added.
“We always look at all errors and decide what to learn from them and how that carries across to other aspects of what we do.
“There were some problems with the software so we fixed some bugs that were in that, changed some of our communications and freed up some of the people involved so they would have a bit more capacity, so there are are changes.
“I want to point out that there has been a story that I don’t think this was a big deal.
“Of course it is a big deal, the point I was trying to make is that it was a single error, a small error that had big consequence but I stand up for my team of guys who have made very few errors over the last few years, just to put that in context Formula One is a complex business and there are things to get right and most of the time we do that.”
With the rain falling heavier following Hamilton’s incident no further action took place on track.