Dec 29 (Reuters) - Four-times cyclocross world champion Mathieu van der Poel will miss at least two races due to a back injury, his team Alpecin-Fenix said. The Dutchman returned to competition with a second-placed finish at the World Cup event in Dendermonde, Belgium on Dec. 26 after recovering from a knee injury sustained in November. But the 26-year-old"s return was short-lived as he was unable to finish a race in Heusden-Zolder the following day, dropping out after six laps due to back pain. Alpecin-Fenix said that medical examinations revealed a "swelling on an intervertebral disc" and that Van der Poel would miss a race in Loenhout on Thursday and a World Cup race in Hulst on Jan. 2. The team did not give a timeline for his return. "The problem has been there for some time, and I"m somewhat relieved that there is an identifiable cause that can be remedied with extra rest and treatment," Van der Poel said. The 2022 cyclocross world championships will be held in Fayetteville, United States on Jan. 29 and 30 but Van der Poel said he was focused on getting healthy. "I want to fully recover first, without time pressure," Van der Poel said. "I will therefore only resume competition when I"m completely ready. If I make it to the world"s, that"s all the better."