And O'Shea says Fernandes, who was signed from Sporting Lisbon in January, has already made an impact at Old Trafford.
The former United defender told the club's website: "[Solskjaer's] had that initial burst when the run was incredible and he went through a few injuries to key players, but Bruno Fernandes coming in seems to have given everybody a huge lift.
"That has coincided with the team going on a fantastic run, looking very threatening again and that is without Marcus Rashford, who has proven to be a big player.
"Unfortunately the unforeseen circumstances have hindered everyone a little bit, especially Ole, but it's a chance for some of the boys who are missing to get back in and be available. That will be a boost for everyone and hopefully, we can push on for that top-four spot."