As a morally upright person that does not like to cheat people, but gambles and has lost a lot of money to gambling in a casino where you have sometimes been cheated even without your knowledge or betting on sports, will you take an opportunity you get and go against your moral standards to cheat a casino or sportsbetting place, just so you can win big at least even once.
Will you try a trick to win on casino game machines if you were told and it is a 100% working trick to cash out? Will you bet on fixed games if you get the tip early?
And let’s be honest, the Saudi league can actually pay him a lot more money compared to what Barcelona can give him right now.
Like you said OP, an upright man cheating is not possible,even though he losses all he had on gambling. If he cheats because he know a trick that is 100% sure,and cheats,I don't think is is worthy to be called an upright man anymore. Gambling is a game of luck and why must one cheat.
When you see gambling as a means of entertainment, you will hardly think of cheating because it wouldn't come to your mind,when you are carried away by the fun. It is people who see gambling an a means to make project that will go to any length if possible to cheat and win big.