Legend of Scottish hero Andy Murray growing

— -- This weekend, we were once again reminded that in tennis, doubles not only matters -- it can matter an enormous amount. It's just one of the great things about Davis Cup, an event that sometimes struggles to get traction with spectators in the U.S.

Granted, the big doubles statement wasn't made in the U.S. or by an American squad -- although the U.S. team that won after an away tie in Uzbekistan to ensure that the nation will remain in the World Group for next year's competition also did nice work.

The spectacular endorsement for doubles was delivered in the World Group semifinals in Glasgow, Scotland, where the Murray brothers (Andy, ranked world No. 3 in singles, and doubles specialist Jamie) outlasted the Australian duo of former singles star and world No. 1 Lleyton Hewitt and journeyman Sam Groth in a five-set epic.

The triumph in the pivotal "swing" match opened the gate to Great Britain's 3-2 win. The country will meet host Belgium in the final.

Like many Davis Cup encounters and few anywhere else on planet tennis, the doubles match in Glasgow had the atmosphere you expect to find at an NFL playoff game or a World Cup soccer match. Even the ubiquitous man in the street in Scotland sat up and took notice.

As columnist Keith Jackson wrote in Scotland's Daily Record: "Strange days these. How on earth did we arrive here at this time and place? A world in which Glasgow is the home of tennis. Where Saturday afternoon stops for a Davis Cup doubles match?"

It's easy enough to explain how the Scots got there. Great Britain hasn't won the Davis Cup since Fred Perry led the squad to its ninth win in 1936. (Does all this sound somewhat familiar?) Andy Murray, who in 2013 became the first British man since Perry to win Wimbledon, is now leading the team on a march to win the Davis Cup again after a comparably long drought.

Murray is fast approaching Scottish national hero status; Braveheart, watch your back!

With the tie knotted at one singles win apiece, the doubles once again loomed critical. Davis Cup may not appear to have a very complex format. There are no more than four and sometimes as few as just two men on the team. There are just five matches: two singles matches on Friday, a doubles match on Saturday and the "reverse" singles on Sunday (with the No. 1 singles players of each team meeting in the fourth of the five matches). But it's surprising how much you can mix and match with four players on a squad.

The three-day weekend format is often criticized because the only event on Saturday is doubles. Why not play a simple weekend format, some ask, like the Fed Cup does, with two singles on Saturday and reverse singles on Sunday -- followed by the decisive doubles (if needed)?

Try this: because that format, while streamlined and perhaps more marketable, is not nearly as compelling. As the past weekend again demonstrated, the Saturday doubles is often always the key that unlocks the door to a win when teams take the court tied at one win apiece. And that makes doubles important in a way it never is anywhere else in tennis.

These days, nearly every team has at least one player capable of challenging the very best player of any other country. So teams often go into Saturday tied 1-1. Enter doubles, in what has come to be called the "swing" match.

This was not a representative Davis Cup year. There were a surprising number of blowout scores, and a surprising number of come-from-behind wins. But of the 14 World Group ties this year (eight teams make up the world group), seven were tied at 1-1 after the first day of play. The team that won the doubles went on to win the tie on four of those seven occasions.

In the World Group playoffs round this weekend, seven of the eight ties were level at 1-1 after the first day (including U.S.-Uzbekistan). The team that won the doubles won six of those ties.

But the numbers don't do justice to the dimensions doubles brings to Davis Cup strategy and planning -- or to the excitement it generates. The team aspect of doubles dovetails with the very idea of Davis Cup, and that familiar "it's only doubles" feeling that haunts the game doesn't exist in Davis Cup. As a result, the drama is as intense and compelling as it is in singles.

On Saturday, the fact that Andy and Jamie are brothers only made the story of their triumph before their home crowd that much more touching. And to top it off, Andy fought off his soreness Sunday to clinch the tie with a straight-sets demolition of Bernard Tomic, which sent Great Britain into its first final since 1978.

It prompted Jackson to write, "Strange as it may seem Scotland is a tennis country now."

You can thank Andy Murray -- and doubles -- for that.