NEW YORK — Wal-Mart is replacing the chief of its U.S. discount stores in what could be an indication of fading confidence that its largest business unit will rebound after more than a year of disappointing results.

Greg Foran, who was promoted to president and CEO of Wal-Mart Asia earlier this year, will succeed Bill Simon, who had been CEO of Wal-Mart’s U.S. stores for four years, effective Aug. 9.

The move announced Thursday marks the company’s biggest management shake-up since Doug McMillon took over as CEO of Wal-Mart Stores Inc. in February. Foran, 53, will report directly to McMillon.

Some analysts think the timing of Simon’s resignation is odd. Wal-Mart, which reports second-quarter earnings results next month, is heading into the two biggest shopping periods of the year: the back-to-school and winter holiday seasons.

“A decision to replace a high-ranking leader of a major retailer before back-to-school and before holidays speaks volumes,” said Brian Sozzi, CEO of Belus Capital Advisors. “McMillon is starting to clean house and pick executives who will move quicker.”

Wal-Mart declined to make either Simon or Foran available for interviews Thursday. But Wal-Mart spokesman Dave Tovar told The Associated Press that Simon’s resignation was mutual. He said Simon and McMillon have been having ongoing discussions about Simon’s departure. On July 18, Simon officially agreed to retire.

Commenting on the timing of the resignation, Tovar said merchandise for the back-to-school and holiday seasons has already been ordered.

“This will give an opportunity for Greg to look at the plan and see if there are any other suggestions for making it better,” said Tovar, who noted that Foran will be taking over the U.S. discount business at a time when the company evaluates its future budget and strategy planning, a three-month period that ends in September.

The leadership change at Wal-Mart’s U.S. stores comes after the division has suffered five straight quarters of sales declines at stores that have been open at least a year. The unit, which accounts for 60 percent of the retailer’s overall sales, has been hurt by a tough economy that has squeezed its low-income customers, along with fierce competition from dollar stores and Amazon.com.

The move to name Foran indicates that Wal-Mart is looking for a different strategy.

Foran, a 35-year retail industry veteran, joined Wal-Mart in 2011 and became president and CEO of Wal-Mart China in 2012 until he was promoted to president and CEO of Wal-Mart Asia this year.

Before joining Wal-Mart, Foran held a number of roles with Woolworths, the leading retailer in Australia and New Zealand.

“Greg is one of the most talented retailers I’ve ever met,” McMillon said in a statement.

Foran follows Simon, who joined Wal-Mart in 2006 as senior vice president of professional Services. He was promoted to chief operating officer for Wal-Mart’s U.S. division from 2007 to 2010. During that time, he created and launched Wal-Mart’s successful $4 prescription drug program.