Director of rugby Jim Mallinder admitted that Northampton's season had taken a hit with the defeat to Racing Metro in the final round of pool matches in the Champions Cup.
Saints qualified for the knockout stages but the defeat - their second to Racing this season - meant they will have to do without a home semi-final.
"It is very disappointing," Mallinder said. "It was a competitive first-half, and we were very disappointed to concede a try just before half-time. And then what you don't want to do is concede straightaway in the second-half, but that sometimes happens. We were chasing the game from then on.
"We came up against a very good Racing team that played well, put pressure on us in our lineout and at the scrum, so we didn't have too many attacking opportunities, and when we did, we coughed up ball. Of course, we are disappointed. We wanted to win today and we wanted a home quarter-final.
"If we have got to go away now to France, we enjoy challenges and we will look forward to that. We have got to refocus. The international players go away now, and we will just get on with it. It is a blow to our season, but we are still in the competition, which is important."
Saints captain Dylan Hartley was yellow-carded by referee Nigel Owens in the 14th minute for tackling an opponent while on the floor at a ruck. It was just his second game back since serving a three-week ban after being sent off against Leicester five days before Christmas.
"Just imagine being me," Hartley said. "I thought I did everything I could to prepare for that game today. I knew the spotlight would be on me. A player runs over me, I put my arms up and tackle him, and the next thing I know I am watching the game."
Reflecting on Wood's early exit less than two weeks before England launch their RBS 6 Nations campaign against Wales in Cardiff, Mallinder added: "Tom Wood twisted his ankle, so hopefully it is nothing more serious than that. He is certainly sore, and we thought it was sensible to get him off."
Racing wing Juan Imhoff scored two tries, with full-back Benjamin Lapeyre and Wales international centre Jamie Roberts also touching down. Scrum-half Maxime Machenaud kicked 10 points via two penalties and two conversions, while fly-half Benjamin Dambielle also added a conversion.
Man-of-the-match Roberts said: "In the first-half we were probably not as clinical as we should have been, but we got two converted tries early in the second-half, and that 14-point swing in a game like this almost did it for us. We retained the ball far better in the second-half, and it is a pleasure to play in this team at the moment.
"We spoke at the start of our season about our goals, and they were to qualify in the Top 14 (play-offs) and Europe. We have ticked one of those boxes today, and to be the only unbeaten team in the pool stages is pretty special. We have got a glorious opportunity now, with a home quarter-final."