It's a natural, linear thing. If you were mathematically minded you could plot the players' progression on a chart which would boast a straight line demonstrating advancement towards some sort of rugby nirvana in the top, right-hand corner of the graph that all players will eventually reach.
It's utter Horlicks of course. Some players improve while others regress and almost all of them do both things at some stage in their career. Confidence and injuries are just two of the biggest influences on form, although who knows exactly why Dan Carter is no better than he was in 2005 and probably never will be whereas Dan Parks is unrecognisable from the player he was this time last season?
Few players demonstrate the see-saw of sporting life quite as well as Glasgow's Johnnie Beattie, who is quite capable of going from champion to chump and back again in the space of one 80-minute match.
He enjoyed great acclaim during the Six Nations and rightly so, hailed by one pundit as the man of the match against England, impressive against Wales and grabbing the crucial, cracking try in Dublin (a score he claims he has still not revisited on video). Against that he was unceremoniously hauled off at the Stadio Flaminio in Rome after just 57 minutes, which was 17 minutes longer than he lasted for Glasgow against Munster last weekend when he made way for Richie Vernon at half time.
"You have to challenge yourself to set targets to play at the top level every week," says Beattie. "Obviously you're not going to be at that level every week but instead of six games out of ten you want to be there for eight or nine games out of ten. That's the difference. That's what I want to achieve."
He is still some way off his target, although no one doubts that the 24-year-old is world class with the ball in hand and his three tries in 12 Tests give him the best scoring ratio of anyone in the Scotland squad. It's an important factor in his favour since Scotland have yet to unearth rugby's answer to Wayne Rooney. I suggest to Beattie that while he occasionally downs tools in the middle of a match, the equivalent of an airline pilot demanding a tea break, at least it ensures he is fresh when the ball finally catches him up, so enabling the No.8 to make those lung-busting line breaks that are his speciality?
There may be some truth in the theory but it is not an excuse he is going to proffer Scotland coach Andy Robinson any time soon. "Err, I don't think that would go down so well." He is probably right but the workaholic English coach may just have rescued Beattie's international career with his own uncompromising brand of tough love. Robinson saw the potential of the athletic youngster with the soft hands and he made Beattie his business, his project, a personal crusade if you like. After winning a meagre four caps in three seasons, Beattie has not missed the starting line-up since the Englishman took the reins last summer.
"It was just good to be involved in the Six Nations," says the man who has spent too long on the outside with his nose pressed up to the window. "It was good to be given a chance, to get just a wee sniff to play in a tournament like that, to get some games. It was a great feeling and I was really excited just to be part of it and get the opportunity."
He nearly didn't and he knows it. Beattie shares a flat with Glasgow colleagues Chris Fusaro, Peter Horne and Richie Vernon and had the latter not been bed-ridden by a bout of glandular fever at exactly the wrong time he might have edged his nose in front of his Glasgow team-mate and landlord, as Beattie concedes.
"It could have all been very different but I wouldn't pin the competition on any one person. There is a huge amount of depth in the back row at Glasgow and that includes players that most fans have probably never heard of. Rob Harley (West of Scotland) has sat on the bench for us and (Heriot's) Chris Fusaro has just signed. They all have their strengths and it's a battle across the field.
"Whether it's (John] Barclay winning the breakdown, James Eddie bringing size and strength, Richie (Vernon] with his speed or Kelly (Brown] who has the all round game. Everyone has their strengths and it's always a fight to try and beat each other at everything."
Glasgow have another sort of fight on their hands this afternoon, one that starts in their heads because the Dragons are to Sean Lineen's team what Kryptonite is to Superman. The Newport team have won the last five league encounters in Glasgow stretching all the way back to 2005, and they have never lost a league match at Firhill. It's an enviable record so talk of Glasgow rolling them over gets Beattie's hackles up.
"The media refer to the Dragons as this weak team that we should beat but people don't give them enough credit because they are a very good team. They humped the Ospreys last week and the Ospreys are a massive team with massive players. Gwent Dragons turned them over fairly comfortably. They are a well drilled side with a very good pack and some real athletes in the backs who can hurt you. People don't understand that. It bugs me because the Dragons are not a bad side.
"Traditionally we have struggled against them at the contact area and the gain-line battle and we need to get that sorted. If we can do that and get some serious ball-carrying going then they won't be able to slow our ball. We've got a real chance of making the play-offs but it will entirely depend upon this game. If we lose this one then I don't think we will qualify."
It's a blunt assessment of the situation but a pretty accurate one all the same. Glasgow have three home matches on the bounce before finishing the regular season with a trip to the Scarlets. Three wins should be enough and, with Leinster one of the home ties, Glasgow coach Lineen would probably rather not have to beat the European Champions to ensure his team's place in the play-offs.
Glasgow's season could depend upon this afternoon's result which, in turn, is hostage to which version of their young No.8 trots on to the pitch come 3.05pm this afternoon; the action man or the spectator? I don't have a clue, Glasgow's coaches don't know and, if it's any consolation, Johnnie Beattie is probably none the wiser than anyone else.