whaa...?? 2 additional friendly matches a day? isn't that too much?
a match will drain your players' stamina 15-20% and normally without rest pack you can only recover (24h/3h) X 5% = 40% condition each day
so 2 matches with 12 hr space are already ideal. no need for additional friendly i think

the best way to prevent injury is rest. no matches.. put players on the bench and no training..