Boro were beaten 2-1 by Bristol City at the Riverside Stadium on Saturday and now have just 11 points from their opening 14 games, with Crystal Palace the only team below them thanks to their worse goal difference.
Mowbray replaced Gordon Strachan during the week with the Teesiders firmly in a relegation battle, but is setting his sights much higher.
"If we can maintain that kind of workrate and keep creating chances like that then we will not lose too many games. But the only statistic that counts is that we lost 2-1," he said.
"The concerning thing is that after they scored the second goal - which was a superb strike - we lost our fluency for a while and it was only in the last 15 or 20 minutes that we started to put the pressure on again."
Bristol City, Boro's conquerors on Saturday, also started the season with ambitions of promotion but were bottom of the table prior to Saturday's win.
"I think we have turned the corner now. We have done well in the last few games, our workrate is good, we have defended well and we look good on the counter. You can see the confidence coming back," said Keith Millen, their boss.
Promotion was probably not on Portsmouth's agenda at the start of the season, but it may be now that they have climbed to within a point of the play-offs.
They defeated Nottingham Forest, but manager Steve Cotterill warned they can only stay up there if they are able to strengthen their squad.
"If we want to be up and around there, we can't run with the squad we've got," he said.
"We had a bench with Richard Hughes, who hasn't trained all week. We had Hermann Hreidarsson who hadn't played for six months. He went on and made a cameo at the end. We need fit boys who can come on and change a game."