Whether Buchanan’s shaky start was down to that knock is unclear, but Bompastor knew her decision was a risk and was willing to act immediately.
Buurman instantly marshalled Shaw, and City’s early threat was quietened as Chelsea regained control and ended the half a goal up thanks to Sandy Baltimore.
Shaw did not record a shot on target and in-form England international Lauren Hemp was quiet as Buurman performed well in a stubborn Chelsea backline.
City manager Andree Jeglertz said he did not think the switch “changed the picture”, but he was outsmarted by Bompastor during the 90 minutes.
Bompastor admitted she had not spoken properly with Buchanan at full-time but promised to “explain myself to her”.
“I just told her a few words. My assistant coach Camille Abily will have done that already probably and I think everything will be fine,” said the Frenchwoman.
“I always have good relationships with the players, bring them clarity, and I’m always direct and honest so they have the information. It won’t be any different.”
The risky substitution was compounded by an injury to striker Melvine Malard 23 minutes later, meaning Chelsea’s XI was tweaked twice before half-time.
Not normally one to bring on players at the break, Bompastor was smart and hooked goalscorer Baltimore, who was likely still buzzing from her impact.
She was replaced by Maika Hamano, who went on to play the ball through to Alyssa Thompson when she was brought down by City goalkeeper Ayaka Yamashita, and she was shown a straight red card as a result, ending the visitors’ comeback hopes.
“We knew going into the second half we only had one substitution slot and we knew Sandy has been playing lots of minutes,” said Bompastor.
“I knew she probably didn’t have the legs to go more than maybe 60 minutes and I knew I didn’t have more slots after that. I was forced into this one as well.
“It paid off and that’s good. Sandy was doing well but she knows the reason why we made that decision.
“That’s the first time I experienced that kind of substitution in the first half. It’s good for my own experience.”
