Van der Poel, winner of the 2020 edition of the cobbled Monument, looked to be the favourite to win this year’s race into the final kilometre, as he faced a two-rider sprint with Deceuninck – Quick-Step’s Asgreen.
But Van der Poel said he was beaten by a stronger rider, as Asgreen sprinted clear inside the final 250 metres.
Speaking after the finish, cyclocross world champion Van der Poel said: “I already felt during the race that he was really strong today and for me the legs were a bit tired at the end so I’m quite disappointed, but I think I lost to a stronger guy today so that makes it easier to accept.
“I think I did a really good race but at the end there was a guy stronger, but for sure I can be proud of of the races I’ve done from the beginning of the season until now but for sure I leave a bit disappointed.
“I started a good sprint. But then immediately I felt that the legs were rough and I couldn’t beat him.”
Van der Poel closed out his Classics season with a second-place finish in Flanders, having won Strade Bianche and finishing on the podium of the E3 Saxo Bank Classic this season.
The Alpecin-Fenix rider looked to be favourite to win the 2021 edition of Flanders when he launched a huge attack on the final ascent of the Oude Kwaremont, 17km from the finish.
Only Deceuninck – Quick-Step’s Asgreen was strong enough to match Van der Poel, with Asgreen trusting his sprint in the final.
Despite his reputation as a long-range attacker, Asgreen was able to beat established sprinter Van der Poel in the final, taking a huge victory for Belgian squad Deceuninck.
Van der Poel said: “I noticed pretty early that Asgreen was the strongest guy from Deceuninck. I checked a few times he was the one who always was quite easily on the wheel, so I knew that he was he was the strongest today from that team.
“Normally when I go to a sprint like this with two guys, I have the best chance but today was there was one guy stronger.”