In professional soccer, both speed and endurance are key physical performance indicators, and while endurance can be tested alone in a high performance lab (VO2max test),  the most accurate on-field performance indicator is The Yo-Yo Intermittent Recovery Test (version 1 & 2) which we talk about here. A study just published in The Journal of Sports Medicine and Physical Fitness demonstrates the ability of The Yo-Yo IR Test to differentiate between professional and amateur football player status, even when no differences between VO2max exists.

18 professional soccer players (mean±SD: age 23.2±2.4 years) and 18 amateur soccer players (mean±SD: age 21.1±1.6 years, VO2max 55.7 ± 3.5) performed both standard VO2max lab test and The Yo-Yo IR Test. The results indicate that while VO2max test values did not differ significantly between professional (56.5±2.9 or amateur players (55.7±3.5 p<0.484), the Yo-Yo IR Test did differentiate. When Yo-Yo tested, pro players covered 966 ± 153m, while amateur players covered significantly less distance 840 ± 156m (p<0.03).

The Yo-Yo IR Test correlates well with VO2max, however it has better predictive ability for high-intensity intermittent performance than a maximal endurance test.