BACKGROUND: Monitoring athlete training effects in team sports requires a systematic approach, adopting frequently implementable methods and sensitive proxy outcome measures able to detect acute and chronic training effects. Consequently, the use of submaximal fitness tests (SMFT) in team sport settings has increased, likely given their time-efficient nature, ease of administration in-season, and strong physiological rationale in observing athlete responses to a standardised exercise stimulus. However, this process has primarily favoured objective measures over subjective athlete responses, and both approaches are yet to be assessed for their respective associations and predictive qualities with maximal test outcomes. AIM: The study evaluated the relationships and predictive qualities between field-based measures of perceived, submaximal and maximal aerobic fitness in a sample of rugby union players. METHODS: Using an observational, cross-sectional approach, 47 high-performance British university rugby union players (21.1 ± 1.2 years; 184.86 ± 7.28 cm; 97.82 ± 14.31 kg) rated their aerobic capacity using a newly modified rating of perceived fitness (RPF) scale, before completing a SMFT (shuttle based, continuous-fixed, 4 min running at 12 km·h-1), and a 1.2 km shuttle run test (1.2SRT) to assess maximal aerobic speed (MAS). Data were analysed using magnitude-based inferences (MBI). RESULTS: An almost certainly [large] positive association between RPF and MAS (r = 0.58; ±0.19) was revealed, with backs reporting a higher RPF (almost certainly [small] increase) and achieving a higher MAS (possibly [small] increase) during the 1.2SRT in comparison to forwards. A likely [small] negative association between SMFT exercise heart rate (HRex) and MAS (r = -0.25; ±0.23) and a possibly [small] negative relationship between RPF and HRex (r = -0.19; ±0.27) was also identified. Regression analysis revealed RPF as the strongest predictor of MAS (R2 = 0.33; SEE: 0.28) compared to SMFT HRex (R2 = 0.06; SEE: 0.35), and both variables combined (Adj. R2 = 0.29; SEE: 0.28), and RPF was shown to be a poor predictor of SMFT HRex as a measure of submaximal aerobic fitness (R2 = 0.04; SEE: 8.48). CONCLUSIONS: Athlete RPF show promising levels of content, face and construct domains of validity in the prediction of MAS measured using the 1.2SRT; however, further work is needed to assess other domains of validity, reliability and sensitivity. Whilst SMFT HRex shows good convergent validity with some field measures of aerobic capacity, HRex is poorly related to or predictive of MAS measured using the 1.2SRT. RPF in its form derived from this study is not well related to or predictive of proxy measures of submaximal cardiovascular/aerobic fitness such as SMFT HRex. The RPF scale used in this study could be a useful monitoring tool in team sports.