Casey Stoney's side suffered two consecutive defeats before the recent international break and starting with Aston Villa "every game is a cup final" for United who sit in the third after leading the league at Christmas.
"We needed the break. The players needed it mentally, to go to a different environment," said Stoney.
"It feels like a very long season in terms of what we've had to deal with covid and the injuries we've had. They’ve come back in a really good, positive space."
Arsenal sit six points behind United, with a game in hand. The two clash on March 19 in arguably their most important fixture in the fight for that last Champions League qualification spot.
"Every game is a must win with our league position, we know that. We have to focus on the process and performance, you can never focus on the outcome," said Stoney.
"If we can focus on that hopefully we can have a good performance on Sunday, take the three points and build confidence going into the Arsenal game.
"The Arsenal game doesn't matter unless we can get three points against Aston Villa."
Tobin Heath was ruled out for 10-12 weeks in mid-January after an ankle injury. Shortly followed another ankle injury, this time for Leah Galton who will likely be sidelined for the remainder of the season.
"I can't hide away from the fact that we've had a lot of important injuries at crucial times, but I won't make injuries an excuse. It's a window of opportunity for someone else."
"It's about those players taking the mantle now, making sure that those that are injured don't miss out on Champions League qualification because they're injured."