David Moyes admits it is proving difficult to get the "right players" into Sunderland before the transfer window shuts because of the rising prices.
Moyes, whose squad has been decimated by injuries, is at least four to five senior players short of the numbers he wants.
Time is against Sunderland as they look to add another striker, right-back, defender and central midfielders to the squad, with the transfer window closing on August 31.
"This is the group of players that's here at the moment, and obviously we've got two or three players with injuries who will come back," said Moyes.
"We'll add to it as well. I've said that. We'll try to improve it.
"We're having to add to it with young players as well as one or two experienced players.
"We've got to try to get the balance right and get the right players in the transfer market.
"That's actually quite difficult because it's easy said.
"It's not that easy and the prices are much higher than they have been in the past."
Lamine Kone's Sunderland future, meanwhile, remains in doubt.
Less than 24-hours after turning down a new contract offer last Thursday, the 27-year-old centre-back turned up to training complaining of a back injury, ruling him out of the Boro game.
Everton last week tabled a bid of £18million for the defender, who had claimed he hadn't been offered a new deal this summer which had been promised to him by the previous regime when he joined in January.
Moyes vowed to honour that promise with the offer of a new contract on September 1.
The club then decided to offer it to Kone earlier, last Thursday, but it was turned down.
"Nothing has changed with Kone since Friday," added Moyes.
Middlesbrough, meanwhile, have picked up four points from their opening two games.
When asked if Moyes expected Boro to be relegation rivals, he said: "I'm not saying they're going to be rivals, but with the surprises you get in the Premier League, you just never know who's going to be up in the top half.
"If you said to Middlesbrough now they'll still be a Premier League team next season, I think they would say they'd be delighted."