Sinclair will skip Canada's two friendlies against the United States this month. The teams meet Saturday in Kansas City, Ka., and Sept. 22 in Portland, Ore.
The Burnaby, B.C., native said, via Twitter, that she needs a break after a busy summer that included the FIFA Women's World Cup in Germany, and the Women's Professional Soccer season. Sinclair was named MVP of last month's WPS final, scoring in the 64th minute to lead her Western New York Flash over the Philadelphia Independence.
Sinclair, who starred for the NCAA's Portland Pilots, tweeted Monday: "Sorry people it is true. I am enjoying my 1st break in 2 years so I can be 100% for olympic qualifiers. Will meet up with nat team in oct."
Vancouver will host the CONCACAF Olympic qualifying tournament in January.
Herdman was hired earlier this month to replace Carolina Morace, who resigned after Canada suffered three losses that resulted in a disastrous first-round exit at the World Cup. He previously served as head coach of New Zealand's women's team.
"We will start to lay the foundation for a fresh start," Herdman said in a release. "We will have a look at our pool of players as well as some of the young players."
Canadian defender Candace Chapman, Sinclair's teammate with the Flash, will also skip the exhibition series.
Herdman's 22-player roster announced Tuesday has 15 players from the World Cup, including midfielders Diana Matheson and Sophie Schmidt, defender Rhian Wilkinson, and 'keepers Karina LeBlanc and Erin McLeod.
Sinclair and Chapman will rejoin the squad for training camp next month. Canada is expected to send a senior women's side to the Pan American Games Oct. 14-30 in Guadalajara, Mexico.
All 21 players from the U.S. team that claimed silver at the World Cup have been named to the roster for the friendlies in what US Soccer has dubbed the "WNT Celebration Series."
The U.S. lost to Japan in the World Cup final.