Speaking at the club's Media Day on Thursday, Hill said that the Cardiff match will allow him to see which combination of players work best for the team.
He said: "After eight weeks of pre-season training the players are all looking forward to getting started and to see where we are on the pitch after all this hard work.
"There will be huge competition for places this season, more so than there has ever been in my time here.
"In previous seasons I would have known my starting line-up by this time of year, but that is now not the case."
Hill is also looking forward to facing former Warriors forward coach Phil Davies, who left Sixways this summer to take over as director of rugby at Cardiff.
"There are some nerves ahead of the first game as there always are. Cardiff are a powerful team and have a great set-up under Phil and it will be great to see him again.
"We have real strength in depth and we will look closely at all positions. It will be a tough time as we analyse everyone to make sure the very best team starts against Bath. Every spot is up for grabs starting on Saturday."
After a tough pre-season schedule Hill will be missing a dozen players against Cardiff through injury.
He said: "We have picked up a few more injuries than we would have liked. We currently have 12 players who are unavailable and we had three from the JP Morgan 7s Series at Gloucester.
"I did want to use two separate squads for these two games against the Welsh sides, but some players will now naturally get more rugby.
"Danny Gray and Andy Short are out as people known and Jake Abbott is also out after he ripped his hamstring.
"He is looking at six weeks which is a blow for him and us. The others will be assessed and we will be able to update people more next week."