Glasgow City suffered a first league defeat in three and a half years as they were hammered 4-1 by Celtic, just three days on from reaching the Champions League quarter-finals.
And head coach Scott Booth said "there's no excuses" for the heavy defeat, despite already having the league title wrapped up.
City had not lost in the SWPL since 2016.
"We just didn't handle the day well at all," Booth told Glasgow City TV.
Natalie Ross gave Celtic a 16th-minute lead before Sarah Ewens scored the first of a double, with her two goals coming either side of Jo Love's counter for the champions.
Josephine Giard added a late fourth for Celtic, who remain three points behind second-place Hibernian but have a game in hand next Sunday away to Spartans.
Stirling University's relegation to SWPL 2 was confirmed after they were defeated 7-2 by Hibernian.
Rangers secured fourth place with a 3-1 win away to Motherwell, while Forfar Farmington drew 0-0 with Spartans.
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SWPL 2 title race goes to final day
The battle for promotion will go to the final day of the season after the top two of Hearts and Hamilton both won.
Hamilton won 5-0 against St Johnstone, and lead the table on goal difference - although Hearts now have a game in hand after their match with the league's bottom side Hutchison Vale was ordered to be replaced.
Hearts originally were awarded a 3-0 win due to Vale being unable to field a team, but they appealed against that decision, pointing out that goal difference could be critical in the title race with Accies winning 19-0 against Vale two weeks ago.
Hearts host Partick Thistle on 17 November at Tynecastle, with Hamilton travelling to Rugby Park to play Kilmarnock.