## 1 Introduction  
Physical development is essential to optimal performance among soccer players [1, 2]. Indeed, previous research aimed at identifying the differences between elite and non-elite professional soccer players has pointed out variables related to the players' physical attributes as the main discriminant factors among competition levels [2, 3].  
The adverse effects of body fat percentage (BF%) on game performance have been consistently described in the soccer literature, particularly regarding sprinting, change of direction, and jumping task performance [4, 5]. BF% was described as one crucial discriminator between players' competitive level among youth soccer players, since elite groups consistently presented a lower BF% than non-elite groups [2]. On the other hand, the body composition analysis of male professional soccer players competing in the English Premier League concluded that there is a slight variation between individuals [6]. In the professional context, little information is available on the body composition of players competing at different levels. The detrimental effect of BF% on speed and agility capacities,which are pointed out as the most predominant actions preceding goals and other decisive situations [7], justifies the need to seek more details on this topic.  
Meanwhile, strength has been consistently evaluated worldwide in sports, which is a significant predictor of performance. Among testing protocols, handgrip emerges as an attribute of elite athletes and a covariate of overall strength [8]. On the other hand, lower-body explosive strength, which is frequently assessed through vertical jumping, has been described as a crucial influencer of sprinting and change of direction tasks [9; 10]. In a study conducted among professional soccer teams from different competitive levels, the authors reported a significant relationship between the teams' success and both the countermovement jump (CMJ) and the squat jump (S) performance [11]. Consistently, the sports literature has suggested that optimizing strength, particularly in the lower body, helps enhance speed and agility [12; 13; 14].  
On the other hand, postural balance is one of the less-studied variables of players' physical development. However, balance is an influencer of performance, particularly in sport-specific skills and injury prevention [15]. Balance is maintained through a complex process involving sensory detection of body motions. Individuals must integrate sensorimotor information and execute an appropriate musculoskeletal response [16]. Postural instability may occur due to increased fatigue, influencing the systems integrating postural control [17; 18]. Previous research has shown that muscular weakness was associated with worse performance in proprioceptive postural control [19]. Moreover, training individuals have a more developed sense of balance than non-training individuals, and the level of playing experience influences postural control performance measures and strategies [20].  
Most of the studies developed among professional soccer players aimed to evaluate differences in their profiles according to their positional roles [6; 21; 22]. There are only limited data concerning the physical characteristics of professional soccer players competing at different levels. However, this information is highly relevant, especially for those who work with non-elite soccer players. Therefore, to close these critical gaps, this study aimed to assess and compare, in detail, the body composition, strength, and balance parameters of elite and non-elite professional soccer players. It was hypothesized that elite players will present superior performance in all variables assessed compared to their non-elite peers.