The Irish province headed to south west France hungry to repeat their 22-14 victory from the previous round in Galway. However, heavy rain showers and an unforgiving pitch played into the hands of an experienced and powerful Biarritz pack and kickers of the calibre of Dimitri Yachvili and Damien Traille.
The French side duly turned the tables on Connacht, running out 17-0 winners with man-of-the-match Yachvili converting tries from Iain Balshaw and replacement Seremaia Burotu. Elwood said: "We had prepared all week and we knew the weather was going to be poor, but we didn't know it would deteriorate like that."
He added: "We knew it was going to be a huge challenge and the conditions did not suit us, but we were in a good space. However, unfortunately if you make mistakes at this level, you get punished."
Elwood acknowledged that it was difficult to establish field position and that Connacht's kicking game let them down, with Dan Parks struggling to exert much influence.
"When you are playing in conditions like that, it's nearly a disadvantage to have the ball. Our kicking game was not at its best today and we got severely punished. We couldn't get the yardage in our kicks and we struggled in that area today. It was disappointing that in the kicking battle we lost out today."
Balshaw's try on the half-hour, coming from a Traille half-break, was the most important score of the game according to the Connacht boss. "It was always going to be a tight game in those conditions, but at 3-0 we were very much in the game. However that defensive error cost us and derailed us," he admitted.
"I think if we had gone in 3-0 at half-time it could have been different, because we would have had the momentum in the second half with the wind behind us. But that score gave them the buffer they were looking for."
Despite the round four loss, Elwood said there was still satisfaction in his young side having beaten the Basque outfit in Galway, if not in Biarritz.
"We take a lot of satisfaction from last weekend's win. We were looking forward to playing on a nice dry track, it would have been nice, but they are a big team and we are not the biggest. It's not our style of play to play into that, and when you have to go toe to toe with the heavyweights, it can be difficult on nights like tonight."