The coach had brought the team within one step of winning the tournament, which made it all the more frustrating.
Literal
Coach [topic-は] team [object-を] tournament championship [to-に] one-more-step [called-という] place [up-to-まで] brought-[concessive-のに] frustrating thing was.
今一歩 ('one more step') marks how tantalizingly close they came. もっていく ('to bring/carry toward') is the directional verb for leading a team toward a goal. ~のに at the end expresses frustrated concession — 'despite having brought them so close, (they fell short).' 悔しい specifically captures the frustration of losing when you should have won.