Background: Peter Forsberg was born in Ornskoldsvik, Sweden, the son of Kent Forsberg, a former coach of Modo Hockey and the Swedish national team. Forsberg was coached by his father for a significant part of his career: the two teamed up from 1991-94 with Modo and later for the national team in the 1996 World Cup, 1998 Olympics and 1998 World Championship, which Sweden won. Forsberg played minor hockey alongside boyhood friend Markus Naslund, who was also born in Ornskoldsvik. Born ten days apart, the two were well-acquainted while playing on separate youth teams before joining together on the regional Angermanland all-star team for the under-16 TV-pucken national championship in 1988.
Context: On 21 January 2011, it was announced that Forsberg had begun training with the Colorado Avalanche in attempt to make a comeback in the NHL.  On 6 February, the Avalanche announced that they had come to terms on a contract with Forsberg worth $1 million for the remainder of the 2010-11 season. Forsberg played his first game back with the Avalanche in Nationwide Arena against the Columbus Blue Jackets on 11 February. He was in the starting lineup at left wing, a departure from his natural center, with 2001 Stanley Cup-winning teammate Milan Hejduk, as well as Matt Duchene. In the two road games he played in, Forsberg was on the ice for 17 minutes and 38 seconds, with zero points and a -4 plus-minus rating. The Avalanche lost both games. After the latter game, Avalanche Head Coach Joe Sacco stated Forsberg was the best player on the ice.  The Avalanche, in the midst of a losing season, heavily advertised tickets for Forsberg's first home game back as a member of the team. However, on 14 February 2011, hours before he was scheduled to play in front of the Avalanche's home fans at the Pepsi Center, Forsberg announced his retirement from hockey. The Avalanche's official website stated that Forsberg would hold a press conference later that day, formally announcing his retirement. In the press conference, Forsberg cited an "inability to defend (himself)" on the ice, with foot problems also playing a role in his decision.  On 8 October 2011, Forsberg had his jersey number retired prior to the Avalanche's 2011-12 season opener at the Pepsi Center.
Question: Why did he do this?. Whats the answer?
Forsberg cited an "inability to defend (himself)" on the ice, with foot problems also playing a role in his decision.