Kenwyn Jones made it three goals in two games with a double in the 3-1 Championship victory over Huddersfield at the Cardiff City Stadium.
But Ole Gunnar Solskjaer said Jones, who was substituted in the final quarter of a comfortable win, is still some way short of full match fitness.
"Kenwyne has been working hard this summer," Solskjaer said after a game also decorated by Peter Whittingham's terrific first-half strike from 30 yards.
"He's still not fit enough to play 90 minutes but he does cause the opposition problems.
"He can get fitter and we're still working on him but he's a big lad and it's hard work.
"It's natural because he came to us in January having played no football whatsoever.
"Right in the middle of a season it's hard to have your pre-season.
"We threw him in and he played a couple of games on adrenaline but his fitness caught up with him.
"Now he's worked this summer, he's had a full pre-season and it's a different starting point for him."
Jones joined from Stoke in a straight swap deal with Peter Odemwingie in January but scored only once in 11 games as Cardiff dropped out of the Premier League.
"It's an important season for him because he was criticised last year," Solskjaer said.
"But it's not easy coming into a struggling club because when you're not 100 per cent fit, you can't be expected to change the whole season around.
"You don't set any goal targets as a striker - I never did - and he just wants to keep improving, getting fitter, keep getting chances and keep telling me that he should be starting."
On the game itself, Solskjaer added: "We started a bit slow.
"They caused us a few problems so I had to switch it around a little bit, but I thought we did that well after 20-25 minutes and then we got the two goals.
"We wanted to get to half-time at 2-0 but there was a little lack of concentration and we gave them a chance, but for me the third goal was the best one."
Huddersfield caretaker-manager Mark Lillis felt the Terriers could get back into the game after Murray Wallace reduced the deficit on the stroke of half-time.
"The third goal was tough to take because we came in at half-time and felt we could get a result," Lillis said.
"But the pleasing thing for me at 3-1 was that we kept trying to play and get back into the game."
Lillis was appointed Terriers caretaker boss for the third time following Mark Robins' shock departure on the back of a 4-0 opening-day defeat to Bournemouth.
But Academy boss Lillis reiterated that he has no desire to succeed Robins on a permanent basis.
"The chairman brought me here two and a half years ago to get stuck into Academy and it's going really well," Lillis said.
"The only thing I want as caretaker manager is to ask them for the same effort and commitment but the new manager - whoever he is - will have a good group of players who will put a shift in.
"Unfortunately we haven't got any points on the board and what happened last week was new to me in football.
"But we've got to get on with it. The good thing is that there is a spirit in the camp and no-one has downed tools."