Manchester United will not be looking to buy and sell "a huge number of players" this summer, according to executive vice-chairman Ed Woodward.
But he insisted there could be more ins and outs than in recent years.
Woodward said: "It's fair to say we are focused on strengthening the squad and looking at some players to sell."
Manchester United were knocked out of the Capital One Cup on penalties by Sunderland
He warned large-scale changes could "destabilise" the team but insisted: "We're not afraid to move in the market in a way we haven't in recent years."
United have struggled following the
retirement of Sir Alex Ferguson
as manager after he guided the Red Devils to the Premier League title last season.
Under new boss David Moyes, the champions are 16 points behind league leaders Chelsea and out of both the
Capital One Cup.
But they are through to the last 16 of the Champions League, where they will face Greek side Olympiakos.
Woodward assumed the responsibilities of chief executive when David Gill departed in the summer after 10 years in the post.
He said: "Historically, we've had roughly three sales and three purchases each year, and it's possible we'll do more than that. It's a dynamic situation.
"We're not in the position we want to be in and we're working hard to change that. We will invest in our squad as needed to make sure we're competing at the highest level.
Juan Mata was David Moyes's only January signing
"Our focus is on building a competitive squad to challenge for trophies. We have the ability to buy players... to make sure we are competing at the top level."
United broke their transfer record in January with the
£37.1m signing of Spain midfielder Juan Mata
from Chelsea, with several players leaving permanently and on loan.
Woodward said: "We are very pleased to have added a world-class player in Juan Mata to our squad, who has already made a positive impact."
United's only major summer acquisition was Belgium midfielder
Marouane Fellaini from Everton for £27.5m,
but he has played just 11 times for the club and has been out since early December following a wrist operation.
The Red Devils face an important month, travelling to title challengers
Arsenal in the Premier League on Wednesday
before the first leg of their Champions League tie with
on Tuesday, 25 February.
When asked how it would affect United to miss out on Champions League qualification, Woodward added: "It takes a long time to build a huge fan base. That will not go away for a long time.
"Some of our competitors have not won the league for a long time and they still sell a lot of shirts globally. So that is not something I am sitting here concerned about."
On Wednesday, United's
financial results for the final three months of 2013
showed revenues rose 11.6% from a year earlier, to £122.9m.