Rees knows that the way in which the visitors slipped away after leading 10-8 at the break means there is plenty to work on ahead of the opening trip to Treviso but he remains confident that they can begin with a bang in Italy.
"We have to look with one eye to next week and, as a squad, we're in pretty good health," said Rees, who welcomed back Richard Hibbard, Ian Evans and Ryan Jones to the matchday party in the West Country.
"We were quite pleased with some of our processes, how we called our line-outs and that we led at half-time. It was good for some youngsters to get game time and for others to get up to speed.
"We were disappointed with the scoreline because we don't like to go down that way, especially the way we did fall off a bit in the second half. Bath had some power we couldn't deal with, and some backs to take advantage of that."
The Ospreys scored the standout try of the game when Ryan Bevington finished off a fine move featuring Dan Biggar, Sam Lewis and Tom Grabham that began on their own 10-metre line but Bath bagged four tries of their own ahead of their Aviva Premiership opener at Newcastle.
The biggest difference between the two teams appeared to be up front, particularly at the setpiece where Bath's experience and extra weight made life difficult for a young Ospreys pack.
Rees admits that improvements will need to be made ahead of what is likely to be one of the most physically demanding tests of the domestic season at the Stadio Monigo but he is backing his forwards to rise to the challenge and then keep progressing throughout the rest of the upcoming season.
"We've got to fast-track to a certain degree because we can't be on the back foot for long periods like we were against Bath," added Rees.
"Treviso have got a driving game to match anyone in Europe so we know we're going to have to deal with it more effectively than we did against Bath. We've got to have a sharp training week and get in better condition for Treviso.
"It's a big learning experience for these forwards, firstly dealing with Bath itself and also some of the intricacies of the technical side (of the scrummage). We're not quite there yet and it's something we're going to have to get right quickly for next week against Treviso, who are equally as powerful up front.
"There will be a fair share of the boys involved against Bath who play against Treviso. Obviously they didn't deal with some aspects very well but it's a learning process."