The Kilmarnock manager is rarely short of a blunt opinion, and he spoke with a mixture of caution and admiration about the man he will face across the Celtic Park dugouts this evening.
Shiels and Lennon are cool towards each other. They come from opposite sides of the old divide in Northern Ireland and, while neither dwells on that, Shiels' attitude on some matters has clearly rankled Lennon.
The Kilmarnock manager admits that, although they are fellow countrymen, he and Lennon do not fraternise.
"Neil and I don't socialise," says Shiels. "In our jobs you don't really have a great social life anyway, but Neil and I aren't in the same social circles. I guess we're a bit cool with each other. We are two completely different beasts. Neil and I might have a drink after a game, but we do it because it is protocol, because of this hospitality thing after a game among managers.
"Sometimes the last thing in the world you want is this situation where you've just been done by a penalty, or you've underperformed, and you have to go and meet the victorious manager. You're standing there thinking: 'I don't really want to meet you.' Neil or anyone else will feel exactly the same if they lose a game. You just feel it is a bit of a pretence."
Shiels, slowly working his way up the managerial ladder, has managed Coleraine, Carrick Rangers and Ballymena United in his time. He compares his own labours at Kilmarnock – managing, coaching, video editing and more – with the infrastructure Lennon posessess at his club, and admits he is envious of what the younger manager has at his disposal at Celtic Park.
Yet he also believes that the real test for Lennon may come when or if he ever has to manage a club without the sense of dominance and resources which Lennon enjoys in Glasgow.
"The one thing I will say about Neil Lennon is, I'm really, really jealous of him," says Shiels. "I'm jealous of him because he is managing one of the biggest clubs in the world and he hasn't really had to go through an apprenticeship. I think that fact might make it difficult for Neil down the line. If or when he does leave Celtic, and he has to manage a club like Kilmarnock or Bristol Rovers or wherever, that is going to be a culture shock for him.
"Look, Neil knows how to do his job, but in one sense the SPL is ridiculous: you've got Celtic and you've got the other 11 clubs. Celtic have already won this league. You've got Celtic players on £20,000-a-week and you've got players at Kilmarnock on £200-a-week, sometimes £400- or £800-a-week. It is absolutely ridiculous. The disparity is unbelievable. The test will be when Neil doesn't have that cushion. But I also believe he is a really intelligent guy, and he might well have that element of adaptability within him."
It is not just around Lennon that Shiels feels a bit of an outsider – this refreshing and engaging Kilmarnock manager appears to have brassed off quite a few rival coaches in his two years so far in Scotland. Yet Shiels insists it is just his style, and that he doesn't go out of his way to pick fights with anyone.
"I think I get on well with all the managers in Scotland," he says. "I think football managers have to have mutual respect. You always know that a rival manager is doing his utmost for his club. Sometimes I kill myself, because I focus too much on how good or how bad my team was, when maybe I should be respecting the opponent a little more.
"I'm also one of those managers who tends to expose people in a roundabout way, unintentionally. I tend to talk about the game and how we should play it, and then I see the other managers having a wee nibble at me, because they're not happy with me. Well, that's just me. Good luck to Neil Lennon, I say. In fact, good luck to all of them."