Chelsea midfielder Mateo Kovacic has come into his own this season

Perhaps Frank Lampard thought that a home game against a Bournemouth, a side that had lost their previous five matches, was a chance to rotate. Even so, the decision to omit Mateo Kovacic was still a surprise. It was a mistake too. As Chelsea's shock defeat at Stamford Bridge on Saturday showed, they are not the same team without him.

Few supporters would have believed that last season. The most notable aspect of Kovacic's first year as a Chelsea player was that he contrived to play 58 games for club and country without scoring a goal. It seemed to sum him up. Talented but ineffective. When Kovacic signed a five-year contract in the summer, the news was met with a tepid response.

But the Croatia international has become a key figure under Lampard, thriving under the coach he has described as the perfect teacher. Even as Chelsea have stuttered, Kovacic has largely escaped blame. At Everton, his first ever Premier League goal offered the team a route back into the game. Against Bournemouth, his prompting from midfield was missed.

2:59 FREE TO WATCH: Highlights from Bournemouth's win at Chelsea FREE TO WATCH: Highlights from Bournemouth's win at Chelsea

It is a turnaround that began almost as soon as Lampard arrived.

"I really liked Kovacic last season, I watched Chelsea a lot," said the manager when speaking on the club's summer tour of Japan. "I saw lots in his game I really liked and what I've found here on this tour from the first day he turned up is a hungry attitude, desire to work and an incredible talent on the ball and I want to work with him and help him improve."

Kovacic has scored twice this season - an improvement - but there is so much more to his game than that and supporters have come to appreciate this. His metronomic passing is an asset. Kovacic has completed more passes than any other midfielder in the Premier League this season. He is able to retain possession in tight situation, keeping Chelsea ticking over.

Crucially, however, Kovacic's passing accuracy of 90 per cent is not just high because he is playing it safe all the time. He is trying to make things happen much more than he did before. "My game is to open spaces for other people," he acknowledged recently. "Now we are more direct, more aggressive, we just try things we did not try last year. I feel better."

Kovacic's passing sonar for the 2019/20 Premier League season

Kovacic's willingness to drive at opponents from midfield was lacking before his introduction against Bournemouth. Consider the opening goal against Crystal Palace when he danced past two men before firing a pass into the feet of Willian, who set up Tammy Abraham to score. Kovacic didn't get the assist but he was the one who broke the lines of defence.

Against Watford, Lampard called him the "worst nightmare" for the opponent because of this ability to penetrate when running with the ball at his feet. Kovacic ranks among the top six players in the Premier League for completed dribbles but the five men above him on the list are all wingers. Running through the middle is more difficult and more destructive.

Kovacic has the feet of a ballerina but the face of a boxer and that combative side has come out this season too. The statistics also show that he is tackling more and winning possession more regularly than last season. Prior to the weekend, no Chelsea player had made more tackles. "He's a very likeable character with a nice tough side to him," say Lampard.

The potential is there to become the complete midfielder. Despite his vast trophy haul at Real Madrid, Chelsea have someone who can still improve and they are likely to enjoy his best years too. Remember that Kovacic is still only 25, younger than Ross Barkley. He might not be one of their own but he can still be a big part of Chelsea's next great team.

Much of the talk during the opening months of Lampard's reign has been of how the new Chelsea boss has been willing to give opportunities to the club's academy talent. There is no doubt that the introduction of Abraham, Mason Mount and Fikayo Tomori has added greater exuberance to the team. The supporters have youngsters to cheer again.

But what this dip in form has underlined is that this isn't just about the kids. Chelsea fans want ones of their own but they want ones who can make a difference too. Kovacic took time to win supporters over, a year as a loan player adding to the sense that he was simply passing through Stamford Bridge, but he is now as admired as Mount in his own way.

After his strike against Valencia recently, Lampard described it as a "project" to get Kovacic scoring more goals. But the sight of his team struggling to find a way past another packed defence at Stamford Bridge on Saturday is likely to convince Lampard that it's the Chelsea project that cannot go forward without the presence of Mateo Kovacic.

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