MARK Warburton may have managed to retain the key members of his Rangers squad during the January transfer window and strengthen by bringing in Emerson Hyndman and Jon Toral on loan.

But the obscene sums of money being spent south of the border, in many instances on decidedly average players, before the signing deadline last night drove home to Warburton that the Ibrox club may not be so fortunate in the future.

The Englishman, whose side take on Hearts at Tynecastle this evening, is under no illusions that the Ladbrokes Premiership outfit will have no option but to sell their outstanding performers in the future.

Read more: Mark Warburton: Rangers have made progress - but the Ibrox club must continue to set realistic targets

“The board will always decide what represents value for the club,” he said. “A lot of players left the club for next to nothing. Our job is, in a cold hearted way, to increase the value of the balance sheet. If we can increase the assets on the balance sheet then all well and good. It is good that players are developing, thriving, getting better and are now assets for the club.

“I hope Rangers fans don’t see it as a derogatory statement. But right now the disparity is such with the clubs down south that we can’t match it. So how do we get money in? If it means you get a good price, which means you get good value for the club, then you have to do it.

“If you sell a player for £8 million and you buy three or four players and move them forward, then that is the way. We have got to move, recognise the gap and respond to it. If that means selling your prized asset at the right time and for the right price, then I am sure they will do it.”

At the moment, that prized asset is undoubtedly Barrie McKay. The Rangers winger has 18 months left on his contract and there is talk of him extending that. But Warburton is certain predatory clubs will be keep tabs on his progress with a view to tabling bids in the future, possibly this summer.

“I wouldn't have been shocked if someone had come in because he's a talented player,” he said. “We saw one session with Barrie McKay and it was a no-brainer for us because of his quality and his technique. He has had to work really hard. We just had him in the office saying that he has got to work even harder again and just push again. I think Barrie can go as far in the game as he wants to go.”

Read more: Mark Warburton: Rangers have made progress - but the Ibrox club must continue to set realistic targets

Rangers are continuing to operate at a sizeable annual loss – which is currently being offset by interest-free loans from wealthy benefactors like Dave King, George Letham, Douglas Park and George Taylor – and the temptation will be great to use any future transfer fees to ease their off-field plight. King has admitted in the past that the business model is unsustainable in the long-term.

Warburton, though, has been assured that money from any transfer fees received will be reinvested in the playing side. “That has been there from day one,” he said. “But we have got to develop the assets first and get the players in, like Josh Windass, like Joe Dodoo, like Jordan Rossiter. They just need time to develop.

“What the manager does is fight the corner. You realise an asset, develop and asset and you sell it. That is the way of the world. But you hope the communication is good, the dialogue is good and the feedback is positive.”

It can, of course, be soul-destroying for a manager to develop a talented player only to have him snatched away by a larger and wealthier rival. Warburton, though, accepts that is the reality of his position.

“That is any manager’s job, that is the way it works,” he said. “MK Dons developed Delle Ali, they picked him up young and then along come Spurs. At Brentford, we looked at him and he was £2 million. Now he is worth £70 million, £80 million, I don’t know. That is the way the game works.

“You have to be comfortable with it. Unless you are Real Madrid, Barca, Man Utd, at the top level, that is the way of the world. So get used to it and keep a production line. You have got to hope that the academy kicks in as well and young boys come through with the attributes to impact the first team and then you sell them. It is not negative to Rangers, that is how we close the financial gap.”

Read more: Mark Warburton: Rangers have made progress - but the Ibrox club must continue to set realistic targets

Warburton, who admitted that he had found it "strange" that such important Premiership games had been scheduled for this evening, enjoyed watching the final hours of the transfer window without having to worry about whether an attempt to sign a player was going to be successful.

“It’s chaos,” he said. "I just can't think of any other industry that would conduct their business that way. None of them has this mayhem. It’s great television, but is shocking when you have to be involved in it and lose out on a player.

"The key for us was to replace the midfield area because we lost Niko (Kranjcar) and Joey (Barton) and Jordan has been injured. So getting the two boys in was important. I always knew about the ability of Emerson and Jon. To get those two was pleasing.”