The former Aston Villa striker swapped Shamrock Rovers for Preston after O'Neill called him into his Ireland squad.
O'Neill said, "Hopefully we played a part in that by calling him into the squad. I'm pleased for the lad.
"It's really up to him now to go there, force his ability into the games. He's got to adapt to their style. Impose himself in the matches, stay in the game for longer and don't drift out for 20-25 minutes.
"Sometimes it's your fault and sometimes it's not. This is a renaissance and well done to Shamrock Rovers and everyone that has given him a helping hand. It's up to him now."