"But we can't keep piling players on top. There will have to be some exits."
Chairman Steve Gibson funds one of the highest wage bills in the Championship, Boro having spent more than £3m during the summer under Gordon Strachan.
And Mowbray admits: "We need to find an equilibrium between salaries.
"Speaking to other managers in the office after the game, we have a very high wage bill for this league, and we have to address that.
"Until we know who might be leaving and what funds will be available because of creating space in the budget, it's very difficult to say 'We'd like to buy him for X amount of pounds'.
"It's something we need to shuffle around. It's a lot of hard work behind the scenes.
"It's looking at a lot of different areas. We'll look at free transfers, we're looking at players from lower league clubs, and some foreign players.
"We need to find a balance, and we're looking at the individual assets of footballers that might help the balance of our club."
There's no contract being signed this week or next week, although we'd love that to happen, but the fans need to know he's been very loyal.
Tony Mowbray on David Wheater's future
Meanwhile the future of Middlesbrough defender David Wheater is still uncertain, as the England under-21 international's contract expires at the end of the season.
The Redcar-born centre-back has played in all but two of the club's 21 league games this season, and remains a key component of Mowbray's plans.
"The whole family are Boro fans," said Mowbray. "They love the club. They're very disappointed to see where we are in the league as we all are.
"He does wish to play in the Premier League and rightly so. His talent warrants that.
"My ideal scenario is that he plays in the Premier League with Middlesbrough and I believe that is his ideal scenario as well.
"His contract is expiring, it's running down. We'll wait and see what January brings.
"We would like to sign him but we will wait until we see what January brings.
"There's no contract being signed this week or next week, although we'd love that to happen, but the fans need to know he's been very loyal.
"I see him in training every day giving his all for the cause. He's giving every ounce of effort to help the cause."
Listen to the full session on BBC iPlayer
Source: BBC Sport
Source: BBC Sport