Competition for places among the party is so intense and so few spots seem to be nailed on certainties that it remains all to play for ahead of tomorrow's fourth tour game against a Combined New South Wales Queensland Country outfit in Newcastle.
"Even sitting around with some of the lads from other countries, we can't pick the Test side," said Murray, who will start at scrum-half at the Hunter Stadium.
"In certain positions we're trying to guess but we really, really can't. There's unbelievable competition everywhere.
"You'd probably guess a few players that might be in already but, other than that, it's really hard to call."
Murray wears the No9 shirt for the second time on the tour on Tuesday, with his previous start coming against the Western Force in Perth.
The Munsterman also came off the bench in the win over the Barbarians and was an unused replacement at the Suncorp Stadium but he faces a big battle to beat Mike Phillips or Ben Youngs to a place in the Test squad.
Phillips picked up the man-of-the-match award in Hong Kong and Youngs impressed in Saturday's win over the Reds but Murray insists that he didn't expect the challenge to be any different on his first Lions adventure.
The 24-year-old intends to make the most of his latest opportunity as he bids to make up for what he calls a 'frustrating' outing in Perth just under a week ago.
"Ben did really well on Saturday. The conditions got tougher as the game went on and I thought he dealt with it really well. There's stiff competition for places, but I've got another chance on Tuesday and I've just got to concentrate on that and do the best I can," added Murray.
"It's just (about) learning our shape, how to control it and guiding the team as best we can. When the conditions got difficult, Ben really altered the game plan towards those conditions. Whatever weather comes up on Tuesday night, I'm going to have to play the right game and guide the pack around the field in whatever way we've been training.
"I was quite happy with the run out I got against the Baa-Baas. Against the Force, it was frustrating. In the first 30 minutes or so, they were really going at our breakdown and coming offside a bit, which stopped things flowing.
"That was quite frustrating, but as the second half wore on, we broke them down, they were getting a bit tired, and we managed to find a bit of space, which was pleasing. But the first half was frustrating for me.
"I'm not trying to do anything different. I'd like to have seen the first half go a little better against the Force, but anytime I go out I'm just trying to play my own game.
"Working with Rob (Howley) is really good. He's been there and done it and he's given me a few pointers and things to work on. Hopefully on Tuesday I can show that.
"People aren't going to get that many more opportunities before the Test series. I presume in a couple of games you'll see the Test side get a bit of time together. As the games go on, your chances are thinning out an awful lot so you've just got concentrate on the time you get on the pitch.
"That's what you're expecting - it's how it was coming out here. You knew you were only going to get a couple of chances to put your hand up and that's what every player was told. We were told that at the very start and we were prepared for that."
The last time The Lions were in Australia, criticisms were made of the amount of training the tourists were doing in the lead up to a Test series they eventually lost 2-1 in heartbreaking circumstances.
The workload was seen as too heavy by some but Murray says that definitely isn't the case this time around.
Head coach Warren Gatland, his assistant coaches Andy Farrell, Rob Howley and Graham Rowntree, and his backroom staff are all keen to keep the players as fresh as possible and that attitude is reflected in the 'quality over quantity' approach to training being seen in OZ.
Murray says Gatland and co understand what's required to get the best out of their squad and the players themselves have embraced the need to keep on learning structures, calls and game plans away from the training pitch.
"Training's been quite similar (to Munster and Ireland), maybe just the structure and timing of training has been different.
"They are a lot shorter sessions - we're on an end-of-season tour so they're looking after us. You're just trying to maintain your fitness, you're not trying to get any fitter. You should be fit enough already.
"There's a lot of work done on the computer and in meetings, talking things out before we actually go out on the pitch. A lot of the work is done, it's just a matter of going through it on the pitch in a short time."