Talks have been underway for several weeks with parent clubs over temporary deals and the Rovers have reportedly reached the stage of verbal agreement for several players.
But Wellens says the players are unlikely to join the Rovers before the start of the preseason as lending clubs are keen to keep them to bolster their numbers with others on international assignments.
“The problem right now is that a lot of these young players from Premier League clubs are very popular and the main players are all at the Euro,” the Rovers boss told Free Press.
“When the Premier League clubs return a lot of these guys will have some playing time in the first two weeks as all the top Euro players will get a few extra weeks off.
“This is why nothing will move quickly in the loan market.
“Premier League clubs will want to sign and date him, but ask that during the first weeks of the preseason players join their first team.
“We are happy with this. We will have our base group and if we drop a few players on loan, I’m happy. “
Wellens confirmed last week that one of his loan signings will be a goalkeeper to face Louis Jones.
The Rovers boss is determined to avoid signing more than five loans.