The Sharks were beaten 20-29 at the AJ Bell Stadium on Saturday following a competitive 80 minutes between the teams.
Despite seeing his side start their campaign with a loss on home turf, Diamond concedes that Bath were the worthy winners.
"Our execution and discipline let us down," he is quoted as saying by Sky Sports News. "Our execution wasn't good and Bath deserved to win today. They were a little bit better than us in the key areas. There was probably a bit of inexperience there in the last 10 minutes."
Sale continue their league campaign next Saturday with a trip to Gloucester Rugby.