Adelaide United coach John Kosmina says he doesn't know if he can keep out of favour striker Sergio van Dijk content at the A-League club.Less than two years after winning the league's Golden Boot award, van Dijk is struggling to get a game at the Reds.Van Dijk was dropped for Sunday's 1-1 draw against Perth while fellow striker Bruce Djite is also battling for game time, coming off the bench for the final 25 minutes against the Glory.Kosmina says it's possible the marksmen could seek opportunities elsewhere.But he wants them to stay in Adelaide and deal with the fact they are in a squad where competition for starting spots is high."It is always hard to keep them happy but that is a fact of life in professional sport," Kosmina said on Monday."You want a competitive squad, you sign good players, you get good players in the squad and then it becomes competitive."I can keep them here and I can be happy, whether I can keep them here and they can be happy is a different kettle of fish."Van Dijk's contract with Adelaide ends on March 31 next year and the Dutch-born striker can negotiate with other clubs before the deal expires.Djite, believed to have attracted interest from Western Sydney Wanderers, is in a similar situation.Kosmina bristled when asked if van Dijk and Djite had long-term futures in Adelaide."What do you call long-term, has any player got a long term future?," he said."We have got 11 players out of contract, Sydney have got 14 out of contract."The average contract in the A-League is 1.6 seasons so has any player in the A-League got a long-term future?"I can knock this on the head now, it seems that you guys (media) at times look for scandal, you're looking for an angle."We are equal top on goal difference ... and we would probably still be top if the Central Coast didn't have a charity event against Sydney two weeks ago."So I don't know what the drama is."Central Coast, who thrashed Sydney 7-2 two weeks ago, and Adelaide head the A-League with 13 points, with the Mariners on top courtesy of goal difference - two goals better than the Reds.