Citi analyst Deborah Weinswig said in a Wednesday research note the split was one of several reasons behind Walgreen's drop in revenue from stores open at least a year. She called the company's November performance disappointing.
Other analysts said the drugstore chain is showing signs of recovery. Prescriptions filled at stores open at least a year fell nearly 3 percent in November. Morningstar analyst Matt Coffina said in a phone interview that figure has been improving since the middle of the year.
"The bigger, underlying story is they seem to be recapturing a fair bit of Express Scripts prescriptions," he said.
Credit Suisse analyst Edward J. Kelly also said in a Wednesday research note Walgreen appears to be doing a better job recapturing the lost business. He said a cutback in promotions by Walgreen and competition also are hurting the drugstore chain's sales.
Total revenue for Walgreen's first fiscal quarter, which ended Nov. 30, dropped nearly 5 percent to $17.34 billion.
Analysts expected, on average, revenue of $17.64 billion, according to FactSet.
Walgreen operated 8,057 drugstores at the end of last month, or 246 more than a year ago.
Walgreen shares climbed more than 4 percent, or $1.43, to $35.70 in afternoon trading Wednesday. The stock has traded between $28.53 and $37.34 in the past 52 weeks, and is up more than 7 percent since the start of the year.