Merga, who narrowly missed out on a medal in the 10,000m at the 2009 world track championships, was still a relatively unknown quantity when he produced a devastating turn of speed to see off a quartet of Kenyan rivals two years ago in Punta Umbria.
The Ethiopian went on to claim a bronze at the 2011 worlds in Daegu but missed out on the London Olympics, a fact he says will help drive him on.
"Last summer was a disappointment. I had some slight injuries in July and lost my chance to go to the Olympics, but since November I have been steadily improving," the 24-year-old told the IAAF.
"Training has been going very well. I feel very strong, very confident and I'm very motivated to do my best to defend the title I won in Punta Umbria two years ago."
But it is Ethiopia's arch-rivals Kenya who have previous form in Bydgoszcz, dominating the 2010 worlds there when Joseph Ebuyer and Emily Chebet claimed the individual senior titles, while the junior races and both team events also all went the way of the east African nation.
And Merga's hopes of victory might diminish given that runners in Bydgoszcz are expected to have to compete in sub-zero conditions, and perhaps on a slippery or frozen course after several days of snow falling on the Polish city.
The Kenyan team features only two who have competed in the championships before: Hosea Macharinyang, who has claimed six top-10 finishes without managing to get an individual medal, and Japheth Korir, third in the junior event in 2010.
Making his international debut in Poland will be the surprise winner of the Kenyan trials, policeman Philemon Rono, who upset the formbook in Nairobi last month and left many of the better-known names in his wake.
The senior women's race has been blow wide open after Kenya's 2011 world gold and silver medallists Vivian Cheruiyot and Linet Masai opted to skip the event to focus on the build-up to the August 10-18 World Athletics Championships in Moscow.
It could come down to a battle between Ethiopian Hiwot Ayalew and Margaret Muriuki of Kenya as the former bids to win her nation's first victory in the event since 2008.
Ayalew finished fifth in the 3000m steeplechase at the London Games but then switched surfaces to take the first leg of the IAAF Cross Country Permit series in November in Atapuerca, Spain, and looks set to threaten the podium in Poland.
Muriuki was victorious in her national trial in Nairobi, which doubled as the penultimate leg of the IAAF Cross Country Permit series, and will be looking to better her sixth place finish at the 2010 world cross.
Chebet will also be back to defend the title she won on Polish ground three years ago, having missed selection for the 2011 edition.
Myslecinek Park, on the outskirts of Bydgoszcz, is the venue for the world cross, and will welcome more than 400 runners from 47 different countries for the one-day event.
Although the park was also the venue for the championships in 2010, runners will doubtless be delighted to discover that the circuit design has since been modified to make the course more challenging, with fewer straights and more hills.
There will be one loop of 1950m which, combined with the start and finish straights, will make up the following approximate distances for the four races: Junior Women - 3 laps, 6km; Junior Men - 4 laps, 8km; Senior Women - 4 laps, 8km; Senior Men - 6 laps, 12km.