Talismanic striker Mullin needed oxygen after goalkeeper Nathan Bishop clattered into him during a friendly against Manchester United in the United States on Tuesday.
The Red Dragons won the match 3-1 but Mullin was diagnosed with a punctured lung after a surprisingly ill-tempered game.
United midfielder Daniel Gore was shown a straight red card for a separate tackle, but Wrexham captain Tozer was reluctant to blame Bishop for the challenge which punctured Mullin’s lung.
Tozer did, however, reveal that Mullin is unable to fly home from the States with just ten days until the start of the League Two season.
“The red card was pretty poor,” the defender told talkSPORT.
“There were a couple of bad challenges. The one from the keeper was probably not that bad but it resulted in a bad injury.
“There were a couple of tasty challenges to say the least.”
On Mullin, Tozer added: “I’d say he misses the start of the season, definitely. I believe he’s punctured his lung. I don’t think he’s able to fly and it’s going to be a big loss for us.
“He’ll come back with the bit between his teeth. We’ll miss him but we’ve got players of real quality who can step in.”
These comments from Paul Parkinson are just as reckless as Nathan Bishop’s tackle was on Paul Mullin
