Following quickly on from the purchase of Salomon Kalou in the summer of 2006, the arrival of John Mikel Obi confirmed Chelsea's determination to add exciting young talent as well as established stars to a squad that had just won back-to-back league titles.
Having smoothed out some rough edges both on and off the pitch, manager Jose Mourinho increasingly used Mikel's talent in the holding midfield role, especially when requiring a longer range of passing than other options including the feted Claude Makelele. As a junior Mikel had played more as an attacking midfielder.
Named Chelsea Young Player of the Year, he survived an injury scare the week before the 2007 FA Cup Final to play the whole game. Chelsea beat Manchester United in the first final at the new Wembley.
The 2007/08 campaign saw Mikel continue to grow in the 'Makelele' role, and by the end of it he had played more games than the old master of the position.
There were hitches. An unfortunate sending off at Old Trafford in Avram Grant's first game was followed by another red card in a Carling Cup semi-final against Everton, his fourth since joining Chelsea.
He started the 2008 Carling Cup final defeat by Spurs shortly after his return from the Africa Cup of Nations but then spent a spell out of the side before ending his second season with responsibility in some important games, including a home win over Manchester United when he was outstanding, although he remained on the bench for the Champions League Final against the same opposition.
Top displays became more commonplace in the 2008/09 season when, with Michael Essien injured for much of the campaign, Mikel became the permanent anchor man - his calm touch a major contribution to the 2009 FA Cup win over Everton.
One item that has remained lacking from the midfielder's game is goals, much like his former mentor Makelele.
Two in his first season, both FA Cup goals in the January of 2007 against lower league opposition, were not added to until September 2013, though as he says, there are plenty of others in the midfield who can contribute goals, allowing him to concentrate on stopping them.
Further injury to Essien in 2009/10 ensured that for the second season running Mikel was the primary choice as deep-lying midfielder. On his return from the Africa Cup of Nations in February he started every game until his own knee and ankle problems in mid-April ruled him out of the season's two-trophy climax, and the first African World Cup Finals. He did however have his first league championship winners' medal.
Mikel's own on-pitch discipline problems are long behind him. He was only booked four times in a Double-winning campaign spent in a highly-competitive area of the pitch.
Carlo Ancelotti revealed he was a similar player in a similar position in his youth but was able to use Essien more in 2010/11 and Mikel spent a period out the side, due to injury and when a 4-4-2 formation was adopted for a period.
Mikel did however pass the 200-game milestone for Chelsea during the season and started all but 10 league games.
The Nigerian began the 2011/12 campaign in Andre Villas-Boas's new-look midfield, starting four of the opening five games, and remained a regular before a thigh injury - sustained against Tottenham Hotspur shortly before Christmas - meant he didn't feature for the Blues for almost two months.
In the second half of the season, however, he re-emerged as a regular in midfield, starting six of our nine games in a busy March and impressing under Roberto Di Matteo with a more attacking outlook, playing more forward passes and dominating from his deep position.
Arguably Mikel's finest performance in a Chelsea shirt was the Champions League Final against Bayern Munich.
Mikel began the 2012/13 campaign in a similar vein to the way he finished the previous one, and was rewarded with the offer of a five-year contract, which he signed early in December, tying him to the club until 2017.
He was an unused substitute in the Europa League final against Benfica.
Mikel scored his first Premier League goal for Chelsea in a 2-0 win over Fulham at Stamford Bridge in September 2013.
Mikel became a squad addition the summer after Chelsea had secured a second straight league title. An agreement had been reached with Manchester United and Norwegian club Lyn Oslo that allowed Chelsea to sign the then 19-year-old Nigerian midfielder for a combined £16 million.
A powerfully-built young man with exceptional ball skills, his standing as one of the brightest young talents in the game had been confirmed at the African Cup of Nations earlier that year, his senior international debut having come in August 2005.
Previously Mikel had starred in the 2005 Fifa Under 20 World Youth Championships where he was voted the tournament's second best player as Nigeria made the final. The player trained with Chelsea for one week in the winter of 2004 and José Mourinho had seen enough to wish to sign him.
The then manager said: 'Everybody was in love, not just me. The players were amazed at a young boy coming and training with us with such quality.
'Later we saw him in the Africa Cup of Nations playing like a giant. He was at an unbelievable level and we know what a player he can be.'
Mikel made his debut for Nigeria in 2005, the then 18-year-old coming on as a second half substitute in a 1-0 friendly win over Libya.
His next appearance for the Nigerian side came against Zimbabwe in the second group game of the 2006 African Nations Cup. Having started the match as a substitute, he made an immediate impression upon coming on, grabbing a goal and assist within 10 minutes. This earned him a first competitive start against Senegal in the final group game, a match which was won 2-1.
His fortunes took a turn for the worse over the next two years, getting suspended for not turning up to an international but then securing a place in Nigeria's 2008 African Nations Cup squad after bridges were rebuilt.
Nigeria were a surprise package, eventually losing to an Essien-less Ghana in the semi-finals. For Mikel there was an unfamiliar role of playmaker just behind the Nigeria strikers and he was their outstanding performer, scoring a goal and making an assist in one game. Injury ruled him out of the 2010 World Cup.
After a lengthy absence, Mikel was recalled to the Nigeria squad for an Africa Cup of Nations qualifier against Liberia in October 2012.
At the tournament in South Africa at the start of 2013, he was one of the senior members of the team at just 25 years of age and was commanding in a more advanced midfield role than his usual club position. Nigeria won the Cup of Nations with Mikel ever-present, beating Burkina Faso in the final.
Mikel played in all three group games as Nigeria were eliminated at the first hurdle in the 2013 Confederations Cup, and scored with a well-taken strike in their 2-1 defeat to Uruguay.