Morgane Metraux of Switzerland entered the day trailing Celine Boutier by five strokes.
At the end of day two of the Olympic tournament, Metraux was up a stroke.
The 27-year-old Swiss golfer got off to a hot start, shooting an 8-under 28 on her front nine. She had two eagles on the front nine. On the LPGA tour, she has one eagle all season.
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A recap of her front nine:
Par-4 first: Birdie (-3)
Par-3 second: Par (-3)
Par-5 third: Eagle (-5)
Par-4 fourth: Birdie (-6)
Par-4 fifth: Birdie (-7)
Par-4 sixth: Birdie (-8)
Par-4 seventh: Par (-8)
Par-3 eighth: Par (-8)
Par-5 ninth: Eagle (-10)
It wasn’t all easy for Metraux. She was issued a "bad time" on the 13th by an official with her group. The first issue does not cost a stroke, but if she were issued another "bad time," it would have been a stroke penalty.
Metraux cooled off and shot a 38 on the back nine, capped by a bogey on the 18th hole after putting one in the water. Metraux shot a 6-under 66 overall.
It was a tale of two days for Boutier. After racing out to a three-stroke lead Wednesday with a 65, she followed it up with a 76. The French golfer is now in a tie for sixth, 3-under par for the tournament.
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World no. 1 golfer Nelly Korda was cruising. She shot even par in round one but was quickly climbing up the leaderboard Thursday.
After birdying the 15th hole, the American had her sixth birdie of the day and was in sole possession of second place. Then disaster struck.
She quad-bogeyed the par-3 16th and bogeyed the par-4 17th. The defending Olympic champion settled down to birdie the 18th hole but ended the day at 2-under and in a tie for 12th.
Lydia Ko, like Korda, shot even par in round one. In round two, the New Zealander shot a 5-under 67 to claim sole possession of third place. Ko won silver at the 2016 Rio Games and bronze in Tokyo.
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The top 10 after the second round:
1. Morgane Metraux (SUI): -8 (66)
2. Ruoning Yin (CHN): -7 (65)
3. Lydia Ko (NZL): -5 (67)
T4. Mariajo Uribe (COL): -4 (70)
T-4. Pia Babnik (SLO): -4 (66)
T-6. Bianca Pagdanganan (PHI): -3 (69)
T-6. Atthaya Thitikul (THA): -3 (69)
T-6. Celine Boutier (FRA): -3 (76)
T-6. Miyu Yamashita (JPN): -3 (70)
T-6. Ashleigh Buhai (RSA): -3 (73)
T-6. Xiyu Lin (CHN): -3 (70)
Round three begins at 3 a.m. ET.
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