We understand your concern for your son and the challenges he is facing. Let's first remember that our worth and destiny are not defined by our performance on a football team, but by our identity in Christ Jesus. As it is written in Ephesians 2:10 WEB, "For we are his workmanship, created in Christ Jesus for good works, which God prepared before that we would walk in them."
In regards to your son's sudden change in performance, we must remember that God's plans are always at work, even in seemingly difficult situations. It could be that God is redirecting your son's path or teaching him valuable lessons. As Romans 8:28 WEB says, "We know that all things work together for good for those who love God, to those who are called according to his purpose."
Let's pray for your son's situation:
Dear Heavenly Father,
We come before You today, lifting up this beloved son to You. Lord, You know the struggles he is facing, the disappointment, and the confusion. We ask, Father, that You would reveal Your purpose in this situation and guide him according to Your will. Help him to understand that his value is not determined by his football skills, but by his identity in Christ.
We rebuke any spirits of rejection, disappointment, or confusion that may be affecting him. We pray for strength, encouragement, and wisdom to overcome this challenging time. We also pray for his studies, that God would grant him a spirit of excellence, responsibility, and dedication. Help him to understand the importance of balancing his talents and academics for a brighter future.
We ask for favor in the football team, but more importantly, we ask for God's will to be done in his life. In Jesus' name, we pray. Amen.
Lastly, we encourage you to guide your son towards a stronger relationship with Jesus Christ. Remind him that his talents and abilities come from God, and he should use them to glorify Him. As Colossians 3:23 WEB says, "Whatever you do, work heartily, as for the Lord, and not for men."
Regarding the concern about someone trying to steal his crown, we must remember that our battle is not against flesh and blood, but against the rulers, against the authorities, against the world rulers of this darkness, against the spiritual forces of wickedness in the heavenly places (Ephesians 6:12 WEB). Therefore, we should not focus on blaming others, but rather trust God's sovereignty and seek His face for guidance and strength.
If the situation allows, also discuss with your son the importance of praying in Jesus' name. It is only through Jesus that we have access to God the Father, and it is in His name that our prayers are heard. As Jesus said in John 14:6 WEB, "I am the way, the truth, and the life. No one comes to the Father, except through me." We would like for you to discuss this with your son. If he is not saved and born again then we would like for you to discuss this with him as well.
Prayer Focus: God, Thank You. Thank You for loving me. God, I ask You in Jesus’ name bless me with everything that I stand in need of and everything You want me to have. Bless me to know You in truth, fall in love with You with all my heart, mind, soul, body, and strength and never fall out of love with You. Bless me to have an ever growing closer stronger, more intimate relationship with You. Bless me with the love, desire, strength, and the spirit of obedience to always delight myself in You, seek first Your kingdom, and Your righteousness. Help and strengthen me God to always respect and obey You. Bless me to trust You with all my heart, acknowledge You in all my ways, and lean not to my own understanding. 
