For the past two major global championships, two names have figured prominently – Americans Jeremy Wariner and LaShawn Merritt. That situation hasn’t changed this year, but unlike prior to the 2007 World championships and to a lesser extent last year’s Olympic Games, the role of favourite has been reversed.

Since his commanding victory in Beijing last year, Merritt, 23, has steadily taken over the leader’s role in the event, despite not having knocked heads with Wariner yet this season. Merritt, who took silver in Osaka with his first career sub-44, will arrive in Berlin with five of the season’s eight fastest performances, capped by two at 44.50, the year’s fastest. Although he hasn’t been as fast as he was at this time last season, it’s worth pointing out that he was never seriously challenged in any of his six appearances over the distance. In Monaco, his last race before Berlin, he won by more than half a second.

Wariner, the two-time defending champion, will also come to Berlin undefeated in six races in the 400 this year. But on paper, the 25-year-old Texan is clearly lagging behind his mid-summer form of seasons past. He has a 44.66 season’s best, but that came nearly two months ago in Carson. After a pair of mediocre outings – 45.74 in Lingnano and 45.28 in Paris – he returned to sub-45 territory with a 44.83 run in Stockholm. But like Meritt, he too hasn’t been seriously tested yet in 2009.

In 2008 the pair engaged in one of the sport’s marquee rivalries, with Merritt taking a narrow 4-3 edge. Each of their personal bests – Wariner’s 43.45 in Osaka and Merritt’s 43.75 in Beijing – came when the pair battled it out. Their first meeting last year was on Berlin’s Olympic stadium track, with Merritt winning by just 0.04 in 44.07. In their last meeting, Merritt again prevailed, but it couldn’t have been closer, 44.50 to 44.51 at the World Athletics Final in Stuttgart. Will a similar scenario play out again in Berlin?

Behind them, the battle for the perceived remaining medal is too close to call. In all 14 men have dipped under 45 seconds this year, but besides Merritt, none have done so consistently.

Going back to the 2004 Olympic Games, the US has swept the medals in all but one of the four global championships. Backing up the big-two this time around are Gil Roberts and Lionel Larry. At 20, US championships runner-up Roberts is the least experienced of the quartet, but does bring noteworthy credentials with him. The student from Texas Tech won the Big 12 conference title in 44.86 in late May and has been resting from his busy collegiate campaign since his 44.93 at the US trials. Larry, fourth at the trials, will make his second straight World championships appearance – he didn’t finish his opening round race in Osaka - but has yet to dip under 45 this season.

Others to watch include Bahamian Chris Brown (44.81, '09), who was fourth in Beijing and at each of the last two World championships; Irishman David Gillick, who improved the national record to 44.77 last month; and Frenchman Leslie Djhone (44.99 ’09), who was fifth on Osaka and reached the finals in two of the last three World championships.

Bob Ramsak for the IAAF