NEW ROCHELLE, New York (Ticker) -- Kathryn Marshall and Korea's Minny Yeo are the improbable leaders entering Friday's second round of the Sybase Big Apple Classic.

Marshall birdied her final hole Thursday to cap a 3-under-par 68 and grab a share of the lead with Yeo on Thursday.

A 35-year-old from Scotland, Marshall had sole possession of the lead before bogeying the seventh and eighth holes -- her 16th and 17th of the day -- at the Wykagyl Country Club. But she lofted a sand wedge to two feet at the par-4 ninth and made the easy putt to join the unheralded Yeo atop an impressive leaderboard.

Yeo entered this tournament only after countrywoman Se Ri Pak withdrew. She made the most of just her ninth round on the LPGA Tour this season with five birdies and two bogeys.

Sherri Steinhauer, the 1999 champion, opened with a 69 and is tied for third with Kelli Kuehne, Kris Tschetter and Italy's Silvia Cavalleri.

Australia's Karrie Webb shot 1-under 70 and is part of a 10-way tie for seventh place. It's another stroke back to Sweden's Annika Sorenstam and 21 others. Sorenstam leads the LPGA Tour with six wins, $1.8 million and a 68.80 scoring average.

While Sorenstam has been on a season-long roll, Marshall has missed three straight cuts since tying for 15th at last month's Evian Masters.

Marshall started on the back nine and made birdies at the 11th and 18th holes. She also birdied a pair of par-3s -- the 160-yard second hole and 197-yard fourth -- before running into trouble at the par-3 seventh.

Yeo also bogeyed No. 7, but that followed back-to-back birdies and dropped her to 1-under. The 30-year-old California resident rebounded with a 10-foot birdie at No. 8 but gave back the stroke with another bogey at the par-4 11th hole.

Yeo had trouble off the tee at the 14th and 18th holes but recovered to make birdie putts of 20 and seven feet, respectively, to reach 3-under.

The par-71 Wykagyl Country Club is a 6,161-yard layout.

First prize is $142,500.