The Objective: This study aimed to evaluate, at two time points (the 1st and 14th training days), the effects of training provocation on thermal asymmetry in football players with and without a lateral ankle sprain (LAS) injury history. Methods: Twenty-seven football players from the U-19 squad of a Turkish Süper Lig club were included. Athletes were divided into two groups by injury history: with LAS injury history (n = 10) and without LAS injury history (n = 17). On the 1st and 14th training days, pre-training and post-training infrared thermographic images were obtained. For the ankle, patellar tendon, calf medialis, calf lateralis, and tibialis anterior regions, the side-to-side temperature difference (ΔT) and the post-training change (ΔPost–Pre) were calculated. Results: On the first day, athletes with LAS injury history showed a marked increase in ΔT at the ankle (+0.19 ℃) and patellar tendon (+0.22 ℃), whereas a decrease was observed in the control group. On the fourteenth day, ΔT values were elevated from pre-training in the injury-history group and expanded toward the calf muscles (calf medialis +0.07 ℃; calf lateralis +0.06 ℃). Tibialis anterior exhibited a decrease in both groups. Conclusion: In football players with LAS injury history, thermal asymmetry that emerges acutely at the joint–tendon level with training load extends to the muscle level over two weeks. This pattern indicates lasting alterations in neuromuscular control and load distribution. AI-assisted thermography can sensitively reveal such asymmetries and may serve as a valuable tool for individualized load management and injury prevention strategies during return-to-play.