There is, however, always a window of opportunity. When your stock is at its highest, it can be time to consider using it to your advantage. Terry Butcher and Steve Lomas anyone?
However, when it comes to cherry-picking, the most covetous eyes are focused on Neil Lennon, his exploits in the Champions League catching the imagination and attention of many club chairmen. Most only see the results. Some might also notice the effort and work that goes into achieving them.
For the people who work with this 41-year-old, in only his third full season as a manager, the motivation, determination and ability to learn are clear. Which is why the first-team coach Garry Parker predicts the best of Lennon has still to be come, and will be worth the wait.
"I've worked with some good managers, Cloughie [Brian Clough], [Martin] O'Neill, and there's nothing stopping him going on to become as good as them," is his honest assessment. "He's that good, and getting better all the time. The way he is with the players, his ideas and everything about him, he can go all the way to the top."
Fortunately for Celtic, Lennon considers this an upward journey he can make without having to leave Parkhead. Not for the foreseeable future, at any rate. That said, it would be folly to take him or his permanency for granted.
It was in the summer of 2010 Parker got the call from his former Leicester City team-mate to come north and, along with Johan Mjallby and Alan Thompson, help the managerial rookie rebuild an ailing slide.
"I was quite surprised with how good he is," admitted the former Aston Villa and Nottingham Forest midfielder. "The way he speaks to people and everything about him, his knowledge. He's just a pleasure to work with. Neil is a leader. He always was. He's a moaning t***, let's put it that way, but that's what makes him a winner. You can see that he can go all the way. He's got that in him.
At 39, Lennon found his way from the relative obscurity of coaching the development squad to the manager's chair and, despite some difficult low points along the way, is now at a career high. It has given him confidence and that most important thing of all, respect. Lennon has proved to be a quick learner and this is best illustrated when he is managing his resources.
Parker explained: "If someone's not pulling their weight, he'll tell them. He's not frightened to do that or leave someone out. He's strong. At the same time, if you are doing it for him, he'll look after you. It was exactly the same as I had under Cloughie and O'Neill. You do it, you play well week in, week out, you stay in the team. If you don't, he'll soon tell you. He's straight with people, tells them how it is. But he's highly respected as well among the lads. I think we all are."
That respect is permeating England and beyond as the European run has shone the spotlight back on a club which had been in danger of drifting into the shadows.
Centre stage is Lennon himself who has put the dark days of the threats to his own security behind him. While the high-profile manager was the target for the cyber-space abuse and real-world parcel bombs, requiring 24-hour protection and police intervention, Parker could only provide moral support.
Did he think his boss and friend might walk away? "You worry about that because he's put up with a lot. But he's that strong a character he didn't want anyone to get the better of him. You worry about how he might react, but I knew deep down he wanted to get the job done and we'd be here for longer, anyway. "
Success in the Champions League is proving a double-edged sword, as it has put Lennon's name on the lips of those who would like him to sprinkle a bit of his low-budget magic on their team. Parker says they might have to cast a spell to get him: "He's got Celtic in his blood. It's his club, isn't it? He wants to win the league, then qualify for the Champions League as often as he can. It would take an awful lot for him to leave. If a really big club came in for him I think he'd consider it, but not until he's completed the job he wants to do here. He just wants to make Celtic big in Europe."
There is a caveat, however, and one which should not be dismissed lightly. "We've got Hooper, Wanyama, Forster, Forrest, Matthews, people like that. If we have to sell, then we're back to square one. We've built up such a good team, we want to keep them together. They might want to move down there [to England]. We don't know. It might not be up to Lenny at the end of the day, but it would be a shame to lose them. It's all right selling a player, but you need money to replace them. To find players like the ones we've brought in is very difficult and expensive."
But not nearly as difficult as it would be finding a replacement for Lennon.