Maguire joined the Red Devils in a reported £80million deal from Leicester City and made his first start for Ole Gunnar Solskjaer’s side in their season opener at Old Trafford.
Lining up alongside Victor Lindelof at centre-half, the United defence immediately came under pressure.
Despite Chelsea hitting the woodwork, United struck first with Marcus Rashford hitting home a penalty after he himself was brought down by Kurt Zouma.
Further goals came from Anthony Martial and Rashford again.
Maguire, 26, was keen to force through a deal to come to United but it appears as though his fiancee Fern Hawkins is not delighted with the weather.
“Daddy’s biggest fans”
Fern, from Sheffield, is a regular Instagram user and took a cheeky dig at the rain in Manchester.
She joked: “Why does it always rain in Manchester.”
Fern posted another photo of herself with their daughter Lillie in the stands.
It was captioned: “Daddy’s biggest fans.”
With another pic of Maguire she wrote: “Very big day for you and all our family today!
“Crazy emotions but we are so proud of you. Lillie and I will be cheering you on as always.
“Go smash it babe.”
Fern posted holiday pics during the summer including a trip to Ibiza.
The couple got engaged in February last year and have a daughter Lillie Saint Maguire, born in April.
United reinforced during the summer transfer window also with right back Aaron Wan-Bissaka from Crystal Palace and winger Daniel James from Swansea.
Maguire joined Leicester from Hull for £17million two years ago and made 76 appearances for the club.