Marcus Rashford has been encouraged by England’s coaching staff to modify his style and make better use of his speed in an attacking trio that Gareth Southgate now believes is as accomplished as any strikeforce in international football.

Southgate and his colleagues believe the Manchester United forward could be more effective if he spends less time dropping back to look for the ball and concentrated instead on using his phenomenal pace to get behind opposition defences. The England manager was full of praise for the impact of his three-pronged attack, with Harry Kane flanked by Rashford and Raheem Sterling, in Saturday’s 4-0 defeat of Bulgaria but there was also some constructive criticism for a player who, by Southgate’s own admission, is not perhaps best deployed as an orthodox centre-forward.

“Although we have, for a long time, almost wanted Marcus to be that option as a [No] 9, I’m still not certain that that is where he is happiest and where he does his best work,” Southgate said. “A lot of his development at United was as a wide raider and he isn’t as strong as Harry with his back to goal and holding play up.

“A lot of his best work is in that inside-left channel, coming in off the line, and I don’t think that’s a problem. I just think we have to be aware that’s probably his profile and to get the best out of him they are the areas of the pitch that we need to get him into regularly.

“I think he can threaten teams in behind more. When he opens his legs and he runs in behind defences that’s the last place they want to be. What happened with the penalty [for England’s second goal], that’s what you want to see. Sometimes he wants to come to the ball [when] I’d be happy with that as a defender. We are encouraging our players to use their strengths.”

Gareth Southgate, left, has passed on some words of wisdom to Rashford. Photograph: Julian Finney/Getty Images

The emphasis, according to Southgate, is for Rashford to think more about his game positionally, taking up parts of the pitch where he can take advantage of his speed, rather than working on the areas where he is not necessarily so strong.

“I can remember Kevin [Keegan] trying to get Michael [Owen] to come to the ball and hold it up,” Southgate said. “It was throwing Michael a little bit because his game was to get in behind teams and that’s where his goals had come from.

“It’s hard because a player’s attributes are formed relatively early. You can work on things and improve things, for sure. But, by 18, 19 or 20 their super strengths are there. The other bits, you can hone a bit, or polish a bit, but their outstanding attributes have already developed.”

Kane’s hat-trick against Bulgaria puts him 14th in England’s all-time list of scorers, with 25 goals, while Sterling has scored seven times in his last seven appearances for his country. Southgate was asked whether any other nation had a better strikeforce and replied: “I think they’re as exciting as anything. They possibly don’t because they sometimes don’t view themselves as others do. They have great humility. But we have to remember, as a coaching team.

“Very often it’s easy to work with the team and find what they can’t do well and, whenever we’re judging games, all of us look at what hasn’t gone well. Sometimes you can overlook the brilliant things that they do, that maybe other countries don’t have. And we have [Jadon] Sancho and [Callum] Hudson-Odoi who are going to push, and really push, so I think it is exciting.”

Southgate, preparing for Tuesday’s game against Kosovo in Southampton, also confidently expects Kane to overhaul Wayne Rooney’s record total of 50 goals for England. “It will just be about fitness and avoiding lengthy injuries – things that are out of your control – but everything else is there for him to challenge it.

“There’s a reason that only Bobby [Charlton] and Gary [Lineker] and Wayne have got there [about 50 goals], because it’s such a hard challenge to stay fit, the number one choice, focused and motivated for the long period that you need to be able to get the games and get those goals. But if anybody has that strength of mentality, it’s Harry.”