Saracens, who face Clermont Auvergne in the Champions Cup final on Saturday, cancelled training today due to six of their players being absent at the Lions' "messy Monday" event in London, where the squad received their kit for this summer's tour of New Zealand.
The timing of the meetup was branded "unbelievable" by Saracens boss Mark McCall, but Gatland pointed out that it was decided upon a long time ago.
"I've got to understand where they are coming from, having been involved in the situation, and I understand Mark's reasoning as well. If it had been last week it would have potentially affected 22 clubs. I understand it's a massive week for them. But Mondays tend to be a recovery day. This date has been communicated months and months and months ago. Now I don't know when Saracens got the information," he told reporters.
"But we have told the unions about this date for a long, long time. So we haven't had any requests from anyone to move this date. But I understand the situation, and appreciate the fact that Saracens and Gloucester are releasing their players to us. If they hadn't been released to us that would have been very difficult for a number of reasons. So it does make a difference.
"We're very grateful to Saracens and Gloucester with big games this week for releasing players to us. It does really make a big difference for us. It's exciting, but also a very important day for us. Every Lions squad goes through this organisation day. I've spoken to the most of the players, it's like the first day of school. Everyone's a little nervous, getting to know each other, players introducing themselves."
The Lions' first match of this summer's tour comes on June 3, while the first Test against the All Blacks will be on June 24.