I came across the following sentence. Is the comma before "but" essential?
Chelsea, a big club for many years now, has a habit of producing players with good potential, but most of the academy graduates do not get a chance to play for the senior squad.
Solution 1:
Yes. Observe the following clauses stand alone as complete sentences.
Chelsea, a big club for many years now, has a habit of producing players with good potential.
Most of the academy graduates do not get a chance to play for the senior squad.
Thus to join the two and form a compound sentence requires both a comma and a conjunction.