I've seen teams spend £150 million and get nowhere near the Champions League. It has taken Manchester City a billion to get there. There are no guarantees.

I want players who are always striving to improve.

I like to be able to control which players I'm working with. Because it doesn't matter how good a coach you are if the guys you're working with think they already know it all. You need a response, you need to feel they're trying. I want players who are always striving to improve.

It took me 35 years of being involved at a decent level of football to become manager at a great club like Celtic.

I was a nerd academically. But I was also an athlete and a musician. I never wanted to be shut out of any situation. I think it was that more than anything.

I come from a family that has always emphasized and enjoyed sports - golf, tennis, football, baseball and the rest.

If an athlete takes a shortcut - literally, for example, by running a street that shortens the marathon route by a quarter mile - he or she doesn't have an insurmountable advantage. But it's an unfair advantage, and in a field of equally matched athletes, it's more than enough to make a difference.

It's good to have someone on the tour so close to you - I mean, like, my sister. There is no one closer to me on the tour, so I don't need any other friends than her. We always talk about everything; not only about tennis, but about all the other stuff around tennis.