Ballack's debut for Chelsea came on 31 July 2006, during a practice match at UCLA's intramural football pitch.
Chelsea presented him to the media the following day where the club also gave him his favoured number 13 shirt, worn throughout his career.
Upon doing so, William Gallas, who previously wore the number 13 shirt for Chelsea, was given the number 3 shirt.
This move created animosity between Gallas and the club as Gallas felt that he was underappreciated.
On 27 August 2006, Ballack made his Premier League debut for Chelsea against Blackburn Rovers.
On 12 September, he scored his first goal for the club on his Champions League debut against Werder Bremen.

He received the first straight red card of his career in Chelsea's 1–0 win over Liverpool on 17 September 2006, after being judged to have stamped on Mohamed Sissoko's leg.
Ballack scored his first Premier League goal on 21 October 2006 against Portsmouth at Stamford Bridge with a header.
His first FA Cup goal came in the 109th minute in the semi-final against Blackburn on 15 April 2007.
This goal resulted in Chelsea progressing into the FA Cup final.
He scored eight goals in all competitions for the club in the 2006–07 season, including a free-kick against Everton at Goodison Park, as well as a half-volley against Porto which sent Chelsea through to the quarter-finals of the Champions League.
Throughout his first season at Chelsea, Ballack was criticised for his lethargic performances – for playing as though he had "a huge cigar in his mouth".

On 29 April 2007, Chelsea released a statement on their official website, informing fans that Ballack had undergone ankle surgery in Munich.
As a result, Ballack did not play in the FA Cup final against Manchester United, which Chelsea won 1–0 through Didier Drogba's extra time goal.
This was Ballack's second trophy this season, his first being the League Cup, the final of which he started.
Ballack's debut for Chelsea came on 31 July 2006, during a practice match at UCLA's intramural football pitch. Chelsea presented him to the media the following day where the club also gave him his favoured number 13 shirt, worn throughout his career. Upon doing so, William Gallas, who previously wore the number 13 shirt for Chelsea, was given the number 3 shirt. This move created animosity between Gallas and the club as Gallas felt that he was underappreciated. On 27 August 2006, Ballack made his Premier League debut for Chelsea against Blackburn Rovers. On 12 September, he scored his first goal for the club on his Champions League debut against Werder Bremen.
He received the first straight red card of his career in Chelsea's 1–0 win over Liverpool on 17 September 2006, after being judged to have stamped on Mohamed Sissoko's leg. Ballack scored his first Premier League goal on 21 October 2006 against Portsmouth at Stamford Bridge with a header. His first FA Cup goal came in the 109th minute in the semi-final against Blackburn on 15 April 2007. This goal resulted in Chelsea progressing into the FA Cup final. He scored eight goals in all competitions for the club in the 2006–07 season, including a free-kick against Everton at Goodison Park, as well as a half-volley against Porto which sent Chelsea through to the quarter-finals of the Champions League. Throughout his first season at Chelsea, Ballack was criticised for his lethargic performances – for playing as though he had "a huge cigar in his mouth".
On 29 April 2007, Chelsea released a statement on their official website, informing fans that Ballack had undergone ankle surgery in Munich. As a result, Ballack did not play in the FA Cup final against Manchester United, which Chelsea won 1–0 through Didier Drogba's extra time goal. This was Ballack's second trophy this season, his first being the League Cup, the final of which he started.
Michael Ballack