In retrospect—on second viewing—Mo Farah’s loss in Saturday’s IAAF World Championships 5K final, the last-ever track medal race for the reigning distance king, came with warning signs.

Even before the race, there were concerns about fatigue after the previous weekend’s 10K final, when he survived a pair of last-lap stumbles and held off a contingent of East Africans to win gold. He had never broken 27 minutes in a previous world title race before finishing that race in 26:49, just three seconds off his personal best; afterward, he called the win his “greatest performance ever” in “one of the toughest races of [his] life.”

There were concerns during the 5K, as Farah—typically placid and unruffled by his competitors’ movements—appeared a tad jittery in his pacing, responding to probing surges from the likes of American Paul Chelimo and at times even leading the pack—an unfamiliar and unwanted position for a tactician of Farah’s caliber so early in the race.

And there were glaring concerns in the last lap, which he began by surrendering inside position. Farah never surrenders inside position; something was wrong. And when his face contorted into its telltale grimace, the sign for the last six years that he was about to unleash a thunderous kick, we saw what that something was: That extra gear was slow to deploy and never fully unfurled.

Farah plans to retire from the track to focus on marathons now that the 2017 Worlds, back home in London, are over. It’s a normal transition for any elite distance athlete, and it comes after a normal end to a track career: losing to a younger competitor in a discipline that rewards fresher legs and stronger kicks. The bizarre part for Farah is that his career to this point has been anything but normal, so while a final appearance at a championship-level race usually serves as a formal farewell, Farah’s leave of the track—and his final loss there—comes with his legacy still in flux.

Usain Bolt also lost last week. He didn’t win a gold medal at all, in fact, and managed just a single bronze after losing in the 100-meter final, not racing the 200, and pulling up with an injury in the anchor leg for Jamaica’s 4x100 relay team. Not that it matters for his legacy as the greatest sprinter of all time. The meet’s most symbolic moment in that regard occurred when American Justin Gatlin bowed to Bolt after edging him in the 100—the new gold medalist honoring the man he bested, rather than the other way around.

Bolt’s GOAT status emerges from his dominance of both his peers and historical rivals—in other words, his wins and his times. The medals are plenty in number: He completed the sprint triple-double at three Olympics and three World Championships, with only a 2011 controversial disqualification in the 100 preventing him from adding another (Bolt wasn’t beaten in a championship-level race between 2007 and last week). So are the records: He ran the fastest 100 and 200 in history by laughable, preposterous margins for sprint distances.

Farah, like Bolt, is an all-time great and unprecedented winner, but he possesses only one of his contemporary’s two GOAT-defining prongs. The wins are his, after 10 consecutive title-race wins at the Worlds and Olympics between 2011 and 2017. Nobody before Farah had doubled in the 5 and 10K at consecutive World Championships, and only ’70s Finnish star Lasse Virén matched him in doubling at two Olympics.

The times, conversely, are not up to par, historically. By straight minutes and seconds, he ranks just 16th of all time in the 10K and 31st in the 5K, and his only two world records are in events where the historical competition could be characterized as soft (the indoor 2-mile) and much, much softer (the tongue-in-cheek 100-meter sack hop). The Ethiopian great Kenenisa Bekele, for comparison, holds the world records in the 5 and 10K and just last year ran the second-fastest record-eligible time in the marathon, with a 2:03:03 in Berlin that is more than five minutes faster than Farah’s sole marathon try to date.

He may have the medals, but his lack of historical speed means that Farah’s mythos is more easily pierced with a single loss than Bolt’s. At the very least, his legacy is more difficult to parse. In some respects, he checks all the requisite boxes—the gripping personal background, the signature post-victory celebration, the creeping specter of inevitability late in a race. To find Farah’s intangibles, one needn’t look further than last week’s 10K, which he won with typical panache: He floated near the back of the pack, loped toward the front, waved to the crowd, flitted back toward the middle—and then, as the remaining laps dwindled, secured his spot on the inside rail and held it through the finish line, winning gold five years to the day after he delighted the home British crowd in the same race at the London Olympics.

But his career narrative gets complicated elsewhere—and not just because of his association with coach Alberto Salazar, which has led to various (unproven) doping allegations that Farah decried over the weekend. His very running style was a mix of following norms (his sit-and-kick strategy) and flouting them (his jaunts from front to back and front again during the early parts of a race), and his career reflected that heterodoxy. Farah was a world-class but not world-best runner until his late 20s, making him an outlier in the distance community. He won his first world outdoor title at the age of 28; neither Bekele nor Haile Gebrselassie—the other two runners in the distance GOAT conversation—won any such race at that age or older. He also never really ran for time or seemed to focus on lowering his personal bests, as his predecessors had; all he did was win. Until Saturday, anyway.

That loss was fascinating in part because of its simplicity. Nothing untoward happened; Farah didn’t suffer any ill-timed stumbles; the East African bloc didn’t unveil some long-awaited golden strategy. For a runner who defied easy narrative categorization for so much of his peak, his reign-bookending defeats fit within an uncomfortably common developmental track. In his second-place 10K finish in the 2011 Worlds, he kicked too early, bursting into higher gear even before the bell—a sign of impatience, perhaps, and naïveté as he reached for his first world title. On Saturday, his last-lap falter stemmed from the reverse problem, as he couldn’t accelerate soon enough, leaving him only the length of the final straight to chase down the two motoring Ethiopians ahead of him. Tired legs, likely, or just old(er) ones. Muktar Edris, the race winner, is just 23 years old to Farah’s 34 and was winning golds on the junior circuit at the same time Farah began dominating the professional distance world.

Now, Farah’s career will resemble a more traditional arc, as he follows the distance runner’s guidebook by exchanging the track for the road. He almost certainly will find success in his new terrain. Although his one marathon effort produced a disappointing 2:08:21 result—for reference, the IAAF database lists 321 men who have run 2:08 flat or better—he is an accomplished half-marathoner, and a racer of his talent and tactical prowess should compete at that distance once he modifies his training regimen.

In all likelihood, he’ll quickly lower his time to the 2:05 range and run in the lead pack in a few big races; after gaining more experience, he’ll drop a blazing time and burst through some finish line tape. But traditional marathoning success won’t help Farah’s quest—if it’s a quest he even desires—to move from greatest track distance runner to greatest distance runner, full stop. He needs, once again, to break free of the typical narrative and achieve something spectacular on the road; an Olympic marathon win in 2020, which would tie him for the oldest man to win gold (at 37), might do it, or the world record in a “real” competition that has thus far eluded him.

As he retires from the track, his case for “greatest” distance runner is inextricable from his claim as the “most decorated” distance runner (and even there, Bekele, with his cross-country titles, might have him beat). He has no argument as the GOAT other than his mountain of hardware—and the fact that once he reached the top, it took six years and 10 titles until somebody was able to knock him from his perch.