It starts off calm.

The hunter is patient, lurking, crouching low. He anticipates, watching his opponent, waiting for the perfect moment to release his attack. Although he moves his feet, his eyes remain focused intently on his prey.

And then it happens.

Before the opposition even realizes it’s being followed, the ball is in the back of the net, and the hunter in the blue number 19 shirt is waving his gloved hands in satisfaction. He’s successfully hit his target.

The scene played out 20 times for Chelsea and Diego Costa during the 2014-15 Premier League season. In his first season with the Blues Costa provided the solution to the problem that was Chelsea’s lacklustre strike force.

A ruthless goalscorer by nature, Costa possesses everything Chelsea lacked up top. Skill on the counterattack; pace in one-on-one scenarios; unmatched aggression and catlike movement. They were all the needs the Blues had been looking to fill, and failing, for several seasons. They were the exact traits José Mourinho found in Costa in the summer of 2014.

Despite falling victim to a lingering hamstring injury picked up during his time at Atletico Madrid, the Spanish striker recorded 20 goals in just 26 Premier League matches for Chelsea. In the 2013/14 season, no single striker had managed more than nine.

Costa’s knack for creating chances for himself is undeniable. He scored seven goals in his first nine matches, matching Jack Meredith as the only other Chelsea player to score in his first four league games. He quickly established himself as one of the most potent predators in the league - the man supporters and teammates loved and opponents feared, both for good reasons. His seamless transition to Premier League play helped propel the club to the top of the table, a spot they never relinquished throughout the entire duration of the season.

While his hot start faded as the season wore on, due to injury and the struggle to get back to match fitness, Costa can still be the biggest asset on this Chelsea team, due in large part to his multifaceted role in the number nine position. While he won’t beat defenders and goalkeepers with intricate footwork, he’s more than happy to do so with power and pace - in the air, on the run and in front of goal. He is a menace to centre backs and fullbacks alike, penetrating any spaces which present themselves with confidence and finding channels behind the defensive line or in tight spaces inside the box.

So often, attention is placed on a scorer’s level of artistry in scoring goals. What’s overlooked is the goalscorer’s work off the ball; his attention to detail in the movements he makes to create chances for himself. Beauty is found not only in the finish, but also in the process. And Costa is proof. His propensity for finding open space and his timing are the skills that will continue to set him apart from the rest of league in his second season.

Costa’s production rate is a direct effect of his ability to release at the right moment, to know when to make that cutting run inside or draw defenders deep, creating room for his teammates.

The teammates alongside him were also integral in Costa’s (and the team’s) success. With the likes of Eden Hazard, Cesc Fabregas and Oscar backing him up in Mourinho’s 4-2-3-1, the Blues at their best was something of a dream. Costa’s instincts means that Chelsea’s midfield corps has options. With his spacing allowing for creativity in the centre, the streamlined passing and precision weaving around opponents in the final third usually ended in a goal. Direct play was also a point of success for Chelsea, which is another facet where Costa shines. When distributing the ball, teammates can rely on Costa to retain possession, whether attacking up the middle or with his back turned to goal. His decision making and hold up play, coupled with his movement off the ball, are areas in which he’ll be relied on once more.

Take his goal from Chelsea’s 2-0 thumping of Arsenal. Inspired by a counterattack, Costa worked in between the centre backs and waited for the play to develop through the midfield. When he saw Fabregas open his hips, Costa turned and released, connecting on Fabregas’ brilliant pass over the top and giving the trailing defenders no chance of catching him. It was the perfect picture of the impact the synergy between Costa and his supporting midfield has has on this club.

While Costa’s skills again have potential to be a major threat to the opposition in 2015/16, so too does his mindset. He’s a ‘leave it all on the pitch’ type of player with a bullish personality that often angers and always annoys the opposition. His well-noted fiery persona has won him both admirers and detractors, earning him 11 yellow cards in all competitions last season, including a three-match suspension for the infamous crime committed against Liverpool’s Emre Can. He’s rough, but confident, a style he certainly can thank his street football background for. The passion he brings to the pitch, however, is exactly what every team hopes to possess. More so than any of his teammates, Costa is the spark that can ignite a fire and set the tone, for better or for worse.

That disposition is part of what Mourinho hopes will help awaken his most recent signing, Radamel Falcao. With the tables turned since the days when Costa was following in Falcao’s footsteps in Madrid, it will be interesting to watch how that dynamic plays out. Mourinho will lean on Costa to help Falcao reach success at Chelsea and help him find the level he was hitting before his ACL injury and struggles at Manchester United.

Of the utmost importance is Costa’s health. If he maintains that while improving his match fitness, the 20 goals he scored last season will probably looks like a bad joke. And he will be called upon to do so, with the Blues lacking depth if Falcao fails to improve and Loïc Remy almost as injury-prone as Costa. The team will also look to their top striker in order to succeed in competitions away from the Premier League, where he failed to produce a goal barring a contested effort in the League Cup final. In his seven Champions League appearances, Costa lacked the firepower he showed in league competitions, something that needs to change for Chelsea to avoid another disappointing exit.

Demba Ba was the previous owner of the number 19 shirt, and it’s difficult to imagine less different players. It’s hard not to contrast Costa’s impact in his first season with that of Ba, Samuel Eto’o or Fernando Torres, Chelsea’s 2013/14 crop of strikers, all of whom struggled to find their form with the Blues before exiting. Costa’s lethal performance in his first season is a stark antithesis of the forwards who preceded him. His arrival, a symbolic changing of the guard, will hopefully usher in what the club hopes will be a long period of success with dominant attackers at the ready.

Mourinho made a point of praising his decision in bypassing other strikers in January 2014 and ‘waiting’ for Costa, but now comes the real test — bettering his debut season. Come August, what will be asked of Costa is no small task. But for a hunter disguised as a footballer, it’s all in a day’s work.