PREVIEW-Boost, Pre give hope for otherwise weak Sprint

"They're still seeing churn from the Nextel base due to higher unemployment," said Hodulik.

Atlantic Equities analyst Chris Watts noted that investors have already put their money on bets that Boost will help show improvements in the quarter, as Sprint shares have more than doubled since January. This makes it vulnerable to a sell-off on the day of earnings if results are worse than expected .

Along with expectations for growth in prepaid, Sprint shares have also been helped in recent months by its exclusive agreement to sell Palm Inc's (PALM.O) high-profile Pre phone.

The agreement was announced in January but the Pre will not help first-quarter earnings as it has yet to hit store shelves.

Analysts are hoping that the phone goes on sale before June 9, when Apple Inc (AAPL.O) is expected to announce a new version of its popular and much imitated iPhone.

"It would be advantageous if they were to get that product out in advance of Apple so they're not operating in iPhone's shadow," said Watts.

But several analysts cautioned that Sprint might not be ready to announce a launch date for the phone when it reports results in the morning of Monday May 4.

Analysts, on average, expect Sprint to narrow its quarterly loss by about 22 percent to 14 cents per share on cost cuts even as revenue is seen falling almost 11 percent to $8.3 billion, according to Reuters Estimates.

Sprint shares rose 31 cents, or 7.1 percent, to close at $4.67 on the New York Stock Exchange on Friday. (Reporting by Sinead Carew; Editing by Richard Chang)