A Premier League without Raheem Sterling terrorising defences seems like a distant memory, but it was only the first half of this season that he was barely getting into the Liverpool side. Even with Luis Suarez suspended, Sterling was used sparingly, and only when Daniel Sturridge later picked up an injury was he given a run in the first XI. What a rise it has since been for the winger-turned-No. 10 who now seems not only a certainty but a necessity for Roy Hodgson's World Cup squad.

It was not until October that Sterling ousted Iago Aspas, and even then he was used as a right wing-back - with significant defensive duties - at home to a struggling Crystal Palace. His next appearance of any real significance came nearly two months later in a disappointing loss at Hull City, in which he was sacrificed as Brendan Rodgers tried in vain to swing the game in Liverpool's favour. That defeat was undoubtedly the low point in Liverpool's season. Sterling was peripheral, touching the ball just 32 times, and ineffective when he did get it - completing only 13 passes. In eight appearances up to and including that match, Sterling averaged a WhoScored rating of just 6.56. Few would have then predicted such a meteoric rise for the teenager.

In the days leading up to his 19th birthday, Sterling was fielded on the left at home to Norwich City and that proved to be a turning point. He put in his best display in Liverpool colours, picking up a goal and an assist as he registered an 8.87 mark with WhoScored. He maintained a 94 per cent pass accuracy, played three key passes and completed three successful dribbles as he was left largely to attacking tasks. A run in the team ensued, and shortly before Christmas he was tearing Kyle Naughton and Tottenham Hotspur to shreds in Liverpool's 5-0 win at White Hart Lane that led to Andre Villas-Boas being dismissed.

When Sturridge made his return to action from the bench in the 5-3 win at Stoke City in early January, it was not Sterling that he replaced. In an extremely short period of time, Sterling had grabbed his opportunity and made himself indispensable to Liverpool. Following Sturridge's recovery, Rodgers spent a few games searching for a solution to being able to field the multi-talented quartet of Sterling, Sturridge. Luis Suarez and Philippe Coutinho without sacrificing any of their best assets.

The obvious solution was to go 4-4-2 with Sterling and Coutinho on the wings. Rodgers did this in his very next game - at home to Aston Villa - but this left the team vulnerable on the counter-attack, with the Brazilian coming in field and providing too little in the way of cover for the defensively questionable Aly Cissokho. Jordan Henderson and Steven Gerrard were overrun in the middle, Sterling's attacking influence was compromised, and Liverpool only mustered a 2-2 draw.

Coutinho's adaptation since has been remarkable. He has become a linking, hard-working central midfielder, flanking Gerrard along with Henderson in a 4-3-3 formation, and that has allowed Sterling to play further forward. When playing in central midfield, only Claudio Yacob (4.6) and Lucas Leiva (4.3) have averaged more tackles per game in the Premier League this season than Coutinho (4.25). That has allowed Sterling to form an incisive front three along with Suarez and Sturridge.

While he previously started on the wing, with Suarez dropping deep to fill the space a No. 10 would occupy, Sterling's role has changed in recent weeks, with Rodgers praising the youngster's tactical intelligence. At Old Trafford, Rodgers predicted that Manchester United's defence, lacking in pace, would drop deep to lessen the space in behind them against Liverpool's speedy attack. That prompted him to select Sterling in a role behind his two strikers where the 19-year-old flourished. And against Man City on Sunday, Sterling gave a performance to suggest his future possibly lies in the centre, registering his fourth-highest WhoScored rating (8.86). He is a big game player, indeed, with three of his four best performances on WhoScored coming against Arsenal, Tottenham and City.

Not by any stretch a traditional No. 10, Sterling is a quick dribbler who often likes space to run into. Suarez and Sturridge stretch the game allowing the young England hopeful the room to turn and run at the opposition defence or make central runs behind them. As he showed with his opening strike on Sunday, he is also developing a composure in front of goal that was previously lacking.

His improvement has been incredible. Still so young and yet playing in such a key role for the team looking most likely to win the Premier League title, Sterling will play a vital part in the run-in at the top of the table. Only six months ago he could barely get a game. What a rise it has been.

All statistics courtesy of WhoScored.com, where you can find yet more stats, including live in-game data and unique player and team ratings.