Brumbies playmaker Lealiifano lasted just 45 seconds on debut last weekend after taking a sickening knock to the head when attempting to tackle Jonathan Davies, while Ashley-Cooper suffered a shoulder injury that forced him from the field with five minutes remaining.
With fellow centre Pat McCabe ruled out with a second fracture of his neck, Deans was facing up to a serious reshuffle had his first-choice partnership not pulled through.
"It's great to have them fit. It was pretty challenging circumstances last week," said Deans, who was forced to play openside flanker Michael Hooper at No12 for much of the second half last Saturday.
"I haven't actually asked Christian whether he remembers his time on the ground! It's great to get your first cap but it wasn't a great way to end your first outing. He'll get to experience a lot more this week and he'll get the benefit of that.
"I thought the boys did incredibly well under the circumstances, particularly given that there was a domino effect that from there, to the extent that we ended up with a forward in the backline. For the team to work their way through and put themselves in a position to be able to win that game was remarkable.
"Clearly this week we've had the benefit of some more prep and hopefully we'll have a little more fluency in our game. Christian will be a big part of that.
"Coopy was very sore post-match. He was cleared in terms of anything structural so it was just a matter of getting beyond that discomfort and pain, and he's done that."
One area that wasn't quite so positive for Deans and co this week was the news that star backs James O'Connor and Kurtley Beale were pictured with Lions fans at 3.50am on Wednesday morning following the Lions' clash with the Rebels at AAMI Park.
The Melbourne pair received widespread criticism in the Australian media and Deans admitted he could have done without the situation but insisted that it wouldn't affect preparations for this weekend.
"Obviously that's not an ideal hour. We've had a conversation for sure. It's not best practice in terms of sleeping habits. I understand that they were keen to catch up with their (Rebels) clubmates but I'm sure the senior playing group will be considering whether we need to make it more difficult," added Deans, who says he didn't consider dropping either player.
"They haven't broken any team protocols as such, but obviously it's not best practice. It's not ideal, and I won't be alone in that thinking. They understand that it was too late for them to get to bed. Suffice to say, it wasn't a comfortable conversation."
Beale was in the thick of the action at the weekend as he missed two late kicks that could have won the first Test for the Australians.
Much has been made of whether Beale has what it takes to bounce back from that disappointment given his recent off-field difficulties but Deans is in no doubt that the 24-year-old is now well placed to push on in the second rubber.
"I think Kurtley's a lot stronger now than a couple of years back. I think he's shown that in his response, the way he's taken to his work this week.
"It's a tough circumstance for any young man to experience. It has the potential to affect his self-belief. I think what he has been through in recent times has made him a much stronger character.
"As tends to happen, with the more experiences you get in life, as long as you retain the meaning from them and the learning from them, you're more able to deal with those circumstances. I've got no doubt that Kurtley dealt with the disappointment a lot more effectively than he may have previously.
"He's got a big future but, like every other player in the game, there are potential derailers out there. But from what we've witnessed and what we've seen he's taken a step in recent times."