A stingy defence is behind Adelaide United's rise to the top of the A-League, coach John Kosmina says.The Reds have recorded their best start to a season with five wins, a loss and a draw from seven rounds.And while the addition of imports Jeronimo Neumann and Marcelo Carrusca has added attacking fire-power, Kosmina credits defence as the prime reason for Adelaide's resurgence after winning just five games all last season."Our defence is really, really solid," Kosmina said."We have had four clean sheets out of seven games - clean sheets help you win games, so defensively we have been good."As much as we have turned the ball over at times in front of that defence, those guys have pretty much done their job."The Reds have conceded just four goals this season and triumphed 1-0 at home against Melbourne Heart on Saturday.Kosmina shuffled his defence with right back Daniel Bowles ruled out of the match with a groin injury, replaced by Cameron Watson."I thought Cam did well," Kosmina said."He got thrown into the deep end. He has played right back before but not for quite a while."Cam is a very talented player. He's very comfortable on the ball and we needed him to be, and he kept things ticking over for us and did a good job defensively as well."Four of Adelaide's victories this season have been 1-0 results though Kosmina was unfazed by a lack of multiple goals in games saying his side would ultimately be rewarded for the many scoring opportunities they were creating."The goals will come if you keep making chances. The goals will come if you maintain the process. The goals will come if you keep creating opportunities, looking for opportunities," he said."I think we should have won by more (against Heart), and I'm not being arrogant about that."We played well enough to score a few more goals."We let them in on occasions but it was more about what mistakes we made - when we were tuned in ... we played some pretty good football."