Safin told Russian sports agency R-Sport on Friday that the 25-year-old Safina considers her decision "as a next step in her life."
In May, Safina took an indefinite break from tennis in hopes of recovering from chronic back pain, but was pessimistic about her chances of returning. She said at the time she didn't want to "torture myself and my body any longer."
"She can live a daily life, but can't do sports anymore," said Safin, who added that his sister will take her time before deciding what to do in the future.
"An athlete has lived with sports for 20 years. Now she needs a year to pull herself together, then she will decide. She is only 25 and there's no need to hurry her."
Safina turned pro in 2001 and won 12 titles on the WTA Tour. She first became No. 1 on April 20, 2009, and spent 26 weeks at the top of the rankings. Her back first became a problem in 2009 and she dropped out of the top 20 by the end of 2010.
Safina won silver at the Beijing Olympics in 2008 and was a losing Grand Slam finalist on three occasions.
Marat, who was No. 1 in 2000 and retired in 2009, and Dinara are the only brother and sister in tennis history to reach No. 1.