As the Mubadala World Tennis Championship opens today, the concept of a "glass ceiling" is one that preys on the minds of three players but must serve as a comfort to three more.
Novak Djokovic, Rafael Nadal and Roger Federer constitute three-quarters of a cabal that even fellow tennis professionals refer to as "the Big Four".
David Ferrer, Jo-Wilfried Tsonga and Gael Monfils, also playing in Abu Dhabi this week, make up some of the leading elements of the chase pack, but they seem to suggest that a barrier - perhaps not visible to outsiders - separates the top quartet from everyone else.
The drop from No 4 to No 5 may be only one slot, but at the moment it also seems to be about 10,000 miles.
"I think the first four - Nadal and Djokovic and Federer and [Andy] Murray - are better than the other players," said Ferrer, who is No 5. "They are playing more consistent in important tournaments. They are reaching semi-finals and finals. They have been very good for three years.
"At this moment it's very difficult to become No 4."
The 2011 season was a banner one for the Big Four, collectively. They filled all eight slots in the grand slam finals and collectively won 22 ATP championships, including all nine Masters 1,000 events as well as the ATP World Tour Finals.
"We can say it's a big drop because the top four won mostly every time in the season," said Monfils, who was No 7 in July.
yesterday said he believed 2011 to be his best season, yet he got to No 5 and could climb no higher. He was No 4 for a time in 2007, but he believes he is a better player now than he was then.
The gap is more than a mental one. Murray, the world No 4, has 7,380 ranking points as the 2012 season commences; Ferrer, just behind him in the table, has 4,925 points and Tsonga, the No 6, is on 4,335. Erasing a gap of 2,400 points (and more) does not happen in a week. Or even a month.
This is an era of particularly dynamic and demanding tennis, and top players complain that a crowded schedule can lead to injury and exhaustion. The effect on the world rankings, however, so far has been an occasional reshuffling among the top four. Everyone else? Still looking up through that glass ceiling.
Since February of 2002, only Federer, Nadal and Djokovic have held the No 1 ranking, and the Swiss and the Spaniard monopolised it until July, when Djokovic broke through.
The top spot was not always such an exclusive club. In 1999, no fewer than five men were No 1, when Pete Sampras, Carlos Moya, Yevgeny Kafelnikov, Andre Agassi and Pat Rafter all spent time at the top.
The No 1 ranking changed hands five times in 2003, and four players were involved: Lleyton Hewitt, Agassi, Juan Carlos Ferrero and Andy Roddick.
Then along came Federer and, 237 weeks later, Nadal .
The pursuers hold out hope that the Big Four can be broken up. Said Monfils: "I think that some guys, maybe Ferrer or some of those guys, can beat some of [the top four] and get in there. A couple of them could break in, if they play well."
The tournament in the capital this weekend could help set the stage. The first step to moving up, as Djokovic demonstrated in climbing past Federer and then Nadal, is to begin defeating the players ahead of you.
Ferrer, Tsonga and Monfils have Djokovic, Nadal and Federer in the same condensed tournament. The first three may be only 22-71 in head-to-head duels with the latter trio, but they have a chance to go 3-0 against them at the Abu Dhabi International Tennis Complex.
Victories this week by the guys stuck below the glass may not count in the rankings, but acquiring the habit is the first step to closing the yawning void between No 4 and No 5.