"A couple of weeks ago I was thinking I might have to come back to New Zealand but then the Koiranen deal arrived," said a very happy Cassidy.
"I've known the team for a while as I'm good friends with Daniil Kvyat [former driver with Koiranen, Toyota Racing Series graduate and now F1 pilot] and I was in the same series with him when I drove with Fortec a while ago.
"I've kept in contact with Daniil and got to know the owner of the team, Afa [Heikkinen]. Purely by chance I met him again when I was testing recently for another GP3 team and he asked me if I had any plans for the year.
"It was then I found out one of their drivers had pulled out and they had a spare slot and we quickly put the deal together."
Cassidy has very little time to even organise a race suit, let alone practise before hitting the track and will be at quite a disadvantage to the rest of the field having only tested once. However, he did excel, posting the sixth fastest time and although he may be approaching the race weekend with a bit of trepidation he's very keen to get racing.
"I've had no time to get used to the car and I've got two very strong teammates," he said. "It's going to be a tough year and I'm going to have to get my head down and my bum up and work away at getting up to speed very quickly.
"I'm not expecting to be right up there this weekend, having not tested with these guys before, but the team has a very good reputation and has produced some pretty good drivers. Being quick testing for another Eurocup team [China BRT] helped my confidence a lot and also helped me get this drive."
For the past two years in Europe he's had last-minute deals to do limited campaigns, never really knowing where to settle. With the Koiranen deal in the bag, the young fella can now knuckle down and get on with the business of winning races, and not worrying where the next weekend's drive is coming from.
"What I feel confident about now, and feel more relaxed about, is I know it's a deal for a whole championship and I can settle into a team and work away at building a relationship," said Cassidy.
"In the past it's been about jumping into a car for a one-off race meeting, which hasn't been ideal. I can tell you - it's a great feeling and to be with a team like this is even better. It's going to be tough, I have no doubt about that, but I'm going to give it one hell of a crack."