Saints finished their inaugural Women's Championship season in sixth after an unfortunate 1-0 loss to Sheffield United.
Eastleigh's play-off dreams were shattered with a 0-0 draw to Solihull Moors, where they were made to rue missed chances and a red card to Christian Maghoma.
Katie Wilkinson made the difference for Southampton FC, who stole a win late on against London City Lionesses.
Two goals from set pieces were not enough for Eastleigh to beat Aldershot in a 3-3 National League draw.
Spacey-Cale called Saints' performance against Bristol City a "testament" to their hard work, despite losing narrowly 1-0.
Southampton were stunned by Ffion Morgan's wondergoal in a 1-0 loss to Bristol City at St Mary's Stadium.
An uninspired Saints dominated the midfield but lacked cutting edge, as Durham punished them for missing chances in a 1-0 defeat.
An unfortunate own goal from James Jones kept Eastleigh in the play-off race, as an early quickfire double won the game against Altrincham 3-2.
Theo Walcott scores in the final few minutes to earn Southampton a vital three points
Manager Ruben Selles has likened his training style to “a circle,” and admitted that he has not placed additional focus on attacking.
