Six players were called up by their national teams but only three - right-back Issa Kabore, centre-back Dominic Hyam and striker Kieffer Moore - were fit enough to travel.
Kabore and Hyam - two deadline day signings from Manchester City (loan) and Blackburn Rovers - have been on international duty with Burkina Faso and Scotland respectively, with the latter already back training with his new team-mates.
Moore linked up with the Wales squad after Wrexham beat Millwall 2-0 in the last Championship outing on August 31 with the striker scoring the only goal as Craig Bellamy's side beat Kazakhstan 1-0 in a crucial World Cup qualifier last Thursday, and he was an unused substitute in Tuesday's 1-0 friendly defeat to Canada.
"The lads who came in late, only Ben Sheaf has been with us because of the international call-ups with the other two away," said Parkinson.
"It has been good to get Ben in training with the lads and Dom was in for his first morning (on Tuesday) so it was good to catch up with him.
"Fortunately with Kieffer, the second Wales game is a home one so hopefully we'll get him quickly back up the road and back settled in Wrexham, ready for training on Thursday.
"We are looking forward to getting all the lads back together Thursday and having a general chat with everybody about where we are now.
"There's 25 players now the window's closed, which is a great opportunity for everyone to settle down."
Moore and Lewis O'Brien struck in the second half at Millwall as Wrexham picked up a first league win of the campaign after taking one point from the opening three games.
Two of those matches were at The Racecourse with the Reds losing 3-2 to West Brom before drawing 2-2 against Sheffield Wednesday who came from two-nil down at the break to earn a share of the spoils.
Parkinson is now hoping for a first home victory against Rangers.
"We've done really well at home (in recent seasons) and we're looking to now really get a good feel for our home form," he added.
"We've had some really good spells in both games but there's periods where we've come under a bit of pressure and given the ball away too cheaply, and we've got to be better in those periods."