Cliftonville boss Tommy Breslin has warned Swansea City to be patient if Northern Ireland under-21 international striker Rory Donnelly seals his move.
The Belfast side have from Premier League newcomers Swansea for the 19-year-old.
Donnelly is to discuss personal terms and the Swans will hope to complete the move in the January transfer window.
But Breslin said: "I would have thought getting into their side this season would be too short a time frame."
Donnelly is Irish Premiership title-challengers Cliftonville's 17-goal top-scorer in the Irish Premiership and has attracted interest from a number of Premier League and Championship clubs.
League One Brenford bid for Donnelly but Swansea's second offer for the player was accepted as manager Brendan Rodgers hopes to bolster a strike-force that has scored 16 goals in 15 Premier League games.
But Breslin has urged caution to Swansea supporters demanding an instant impact as the promising teenager is set to swap part-time football for the professional game.
"He's a a young lad who has been playing part-time football," said Breslin.
"So his fitness would need to improve and he would need to build up his strength with the program for full-time players - so he'll need a bit of time.
"But certainly next season, he'll be there to make an impact.
"We're devastated to be losing him but for the lad, it is the opportunity of a lifetime and we couldn't stand in his way of playing professional football.
"We're just delighted we can help accommodate Rory's dream."
Rodgers returned to his native Northern Ireland to watch Donnelly play in Cliftonville's County Antrim Shield win over Glentoran in November.
"He'll go off his left side and his right side," described Breslin.
"He has quite a bit of pace and natural ability. He is creative and scores goal - and obviously every club is looking for a goal-scorer and Swansea have made an offer.
"Who knows whether he will make the step up but he has all the potential and ability.
"Playing professional football is a different environment and I'm hopeful he will do very well and break into the first team."