Chelsea legend Gianfranco Zola says Jose Mourinho must be trusted to diagnose the club's problems in the summer transfer window ahead of the new Premier League season.

Mourinho finished his first campaign back at Stamford Bridge empty handed after finishing third in the Premier League and being knocked-out of the semi-final of the Champions League during a season in which he continually played-down his team's chances.

The Chelsea boss has made no secret over his desire to sign a new striker in the summer window, with the club continually linked with a move to Atletico Madrid forward Diego Costa, and Zola says supporters must trust Mourinho to sign the missing link.

"They did well [last season], said Zola.

"At the end of the day at the end of the season they didn't get probably what they were expecting, but it hasn't been an easy season for anybody apart from Manchester City. Chelsea will certainly do better next season.

"I'm not the manager, I don't want to be right now. The point is they didn't achieve what they wanted maybe because they were lacking something in the team. But it's something that Mourinho knows exactly what it is and they'll try to sort it out.

"Certainly it [in attack] is one area that Mourinho said they need to look for so we'll see what they do."

Strikers Samuel Eto'o, Fernando Torres and Demba Ba came under continual criticism from Mourinho throughout the season as between them the trio scored just 19 times in the Premier League.

Reports have since linked Chelsea with moves to Costa – who scored against them in the Champions League semi-final – and Monaco's Radamel Falcao.

The club signed Mohamed Salah, Kurt Zouma and Nemanja Matic in the January transfer window but will make further additions in the off-season, in order to close the gap to champions Manchester City and Liverpool after Chelsea finished four points off the pace last term.