Darren Ferguson had a warning for his side despite being pleased with their performance in an opening day goalless draw with Gillingham.
Rovers did everything but score against the Gills and Ferguson later admitted it was a case of “two points dropped”.
Matty Blair and John Marquis squandered the best chances, while Ben Whiteman twice went close from distance and Liam Mandeville was only denied by a last- gasp clearance.
Ferguson told his players after the game that they have to expect fewer goalscoring chances in League One - and so have to be more ruthless when they come along.
“In the cold light of day we’ll probably look back and think it was a game we should’ve won,” said Ferguson afterwards.
“Hopefully you don’t have too many of them.
“No disrespect to Gillingham but I didn’t think it was dissimilar to a lot of games last season when we dominated.
“What I’ve said to the players is you won’t get as many chances this season in League One.
“We did get some today. We probably got double that last season. But you’ve got to take one of them.
“We’ve got to be more ruthless when we do get the chances.”
He added: “For the majority of it I was very pleased with the performance. We played some very good stuff, some very good football.
“What we had worked on all week with the shape of Gillingham, the lads did the majority of it really well. But it’s two points dropped.”
Andy Williams was not involved after tweaking his hamstring against Chesterfield and is most likely to return against Blackpool on August 19.
Rovers are still waiting for international clearance for new signing Issam Ben Khemis.
“It can take up to ten days minimum and he signed on Thursday,” said Ferguson.s
“We’re hopeful we’ll get it for the Blackburn game but you’re never too sure.”