Nick Cushing’s side welcome the Solihull outfit to the Academy Stadium in a 12:30pm kick-off with a 100% record from their first five games before the international break.
Christiansen has started the season in fine form, earning deserved praise from her manager after his side sailed through to the Champions League Round of 16.
The midfielder insists neither she or her teammates are getting carried away with the start ahead of the meeting with her former Club - a side who have provided tough opposition in recent years.
“It’s a big week,” she told ManCity.com. “We’ve been working hard on the training pitch and we’re feeling good.
“Of course, my allegiances parted when I left Birmingham and signed for City but they are a Club I enjoyed four very successful years at.
“They’re a great team with really good young players. Evidently, they have a really strong manager who is doing a really good job.
“It’s not going to be an easy game. I expect a really tough team to come and make life really difficult for us by being difficult to break down.
“As always though, we’re focused on ourselves and what we can do to break them down and get three points. Hopefully, it will be an exciting game for the fans.”
On the Blues’ impressive start to the campaign, Christiansen added: “We’ve played five games and won all five.
“It’s important that we’ve set that standard. Moving forward, we’ve got to hit those standards now to keep our momentum going.
“We’ve been playing some really good football and we’ve scored some really great goals. Momentum is huge so we have to keep making sure we stay solid defensively and keep taking our chances.”
Fourteen of City’s first-teamers jetted off for international duty last weekend.
Asked whether the international break arrived at the wrong time for the Blues, Christiansen replied: “It’s a challenge to us as professional footballers to handle the transfer between international and Club football.
“It’s up to us as professionals to ensure we’re prepared for both.
“Coming back into a Club environment, we’re ready to go again after a couple of days of rest.
“Training has been great since we came back in. It’s important our minds are refocused now on getting three points on Sunday.”