And how many games did he use it before he "gave" it to you?
These new balls absorb oil like nobody's business. One guy noticed a loss in reaction in a Violent eruption, a polished pearl, after only 30 games. Dull, sanded balls are subject to more oil than a polished pearl under normal circumstances.
So it could have absorbed enough oil to affect its performance.
Additionally, balls need to have their surfaces refreshed on a regular basis. Some (like balls with a 4000 grit surface) need it much more often than one with a 1000/2000 grit surface. One Storm rep even said that one of their new super-high performance coverstocks should significant wear after only 7 games!! That's crazy, but true.
The first thing I'd try is a surface refreshing. If that doesn't help, then I try an oil extraction.
Of course, all this is extraneous if the real change has been in the amount of oil put down by the house ....