For Redknapp, it has been a case of wondering whether Modric will leave White Hart Lane as Chelsea have sternly tested the resolve of chairman Daniel Levy.
Levy has repeatedly stated the Croatian playmaker is not for sale at any price, and has so far been true to his word in rejecting bids from the Blues of £22million and £27million.
However, the fact Modric did not play in Thursday night's Europa League play-off demolition of Hearts, amidst claims of a thigh injury, has fuelled talk he could leave before the transfer window closes as he is not cup tied for European competition.
The flip side for Redknapp is that he knows with a £30million kitty at his disposal from the potential sale of Modric, he could add to a squad he has barely strengthened over the past few months.
With Spurs due at Old Trafford on Monday, and with rumours Modric could play, Ferguson said: "Tottenham have said they're never going to sell him. That's what Daniel Levy has said.
"But then you've a feeling if someone comes in with the right offer he will be sold, and that's difficult for Harry, to work out Daniel Levy's thinking.
"I know Harry wants to bring in a couple of players, no doubt about that, because what he has achieved the last couple of seasons has been brilliant.
"So it has been difficult for Harry getting through the summer not quite sure what's going to happen.
"It could yet happen before the window closes he gets two or three players in, and I think he's hoping for that.
"I listened to him on the radio saying he could get four players in for the money. That's what he is thinking.
"In other words, giving him a bigger squad to compete in all the tournaments Spurs are in, and to challenge for the Premier League. So he was looking at improving his options."
For Ferguson, his options are very much youth-oriented these days, with one of the youngest teams he has selected for many seasons to take to the Old Trafford pitch on Monday.
With defenders Rio Ferdinand and captain Nemanja Vidic sidelined, Jonny Evans and new acquisition Phil Jones, 23 and 19 respectively, form the centre-back pairing, with 21-year-old Chris Smalling at right-back.
Add in new goalkeeper David de Gea and Danny Welbeck (both 20), Tom Cleverley (22), Anderson (23), Nani (24) and Ashley Young and Wayne Rooney at 25, there is a fountain of youth at Old Trafford these days which excites Ferguson.
With Edwin van der Sar, Gary Neville and Paul Scholes all retired, Ferguson said: "We were always aware we had players who were coming to the end of their careers. That has been on the horizon for us for quite a few years.
"We knew it was going to happen, you don't want it to, but it does and there's nothing you can do about it. Age catches up with us all.
"So we've replaced the players who have left us, and we've still players at the club in their 30s, which is a lot of experience.
"At some point when the young players may hit a pocket there will be enough experience to augment the challenge we're after this year.
"It is a very young team at the moment, but it's one full of energy and of great ability, and I'm enjoying watching them."