Bath director of rugby Todd Blackadder was dealt a double blow as Taulupe Faletau suffered a knee injury during the 24-20 Champions Cup defeat at Toulon.
Wales and British and Irish Lions No 8 Faletau injured his left knee at a ruck in front of his own posts when he was cleaned out in the 48th minute.
"I hope it's not the same knee as he injured last season, but it doesn't look good," said Blackadder.
Bath had the better of the first half but having raced into an early 10-point lead, Blackadder's side were hit with a try from Ma'a Nonu five minutes before half-time.
Toulon turned up the heat in the second half and Chris Cook was sent to the sin-bin and Toulon scored from the resulting penalty scrum.
Jonathan Joseph gave Bath fresh hope only for Anthony Belleau to have the final word and move the French giants three points clear at the top of Pool 5.
"We came here to do a job and when you put in so much effort, and the game was there for the taking, you are a little bit disappointed," admitted Blackadder.
"But we will build on that and we will be better next week. This pool is going to be wide open.
"I am really proud of my guys. We came to play and we did. We created a lot of chances.
"We had a good game plan and we created opportunities. It was an outstanding effort and I'm really encouraged by it and feel really positive.
"There are plenty of encouraging things we can build on for next week. Everyone really stepped up and delivered."