Steve Clarke believes Che Adams will have a long and successful international career after the former England Under-20 international pledged his allegiance to Scotland.
The Southampton striker rejected Scotland's advances in 2017 but Clarke heard a "whisper" last week that the 24-year-old had decided to come on board.
The decision comes in time for Adams to feature in the first three games of Scotland's World Cup qualifying campaign against Austria, Israel and the Faroe Islands this month.
And the former Sheffield United and Birmingham forward has put himself in the frame for Euro 2020.
"He was approached when Alex (McLeish) was the manager four years ago," Clarke said. "He would have been 19/20 on the back of playing a couple of friendly matches for England Under-20s, so it's not as if he's got a long history with England.
"I had a good chat with him a couple of times last week and things moved very quickly and the paperwork has been done.
"It's the right time first of all because he showed an inclination to play for Scotland. That makes a big, big difference.
"We spoke about the future. We didn't speak just about the near future, we spoke about the far future. For me Che, at 24 years of age, can hopefully go on to have a long and hopefully distinguished Scotland career."
Leicester-born Adams – who has a Scottish grandparent – has netted seven Premier League goals this season including three in his last three matches.
"The player himself is excited to be coming to play for Scotland and hopefully the lads in the squad will realise that Che can bring something a little bit different," Clarke said.
"He's an English Premier League striker in good goalscoring form, plays for a good club, plays in a good way. I like his movement on the pitch, he's a strong boy.
"He's not tall but he's good in the air, he can run the channels. He's got a lot to his game that I think will certainly make the squad better and hopefully will make the team better as well.
"And that's what you have always got to try and do. The euphoria of qualifying for the Euros has died down a little bit and now we have to address areas of the pitch that are a little bit of concern."
Former Raith and Dunfermline striker Nisbet arrives after netting 14 goals for Hibs this season.
"I like his movement, I like the way he gets free in the box," Clarke said. "And it's an area of the pitch where we have to keep looking because we need to score more goals."
Clarke has brought in Celtic centre-back Jack Hendry after he rejuvenated his career on loan with Belgian side Oostende, while Grant Hanley, John Fleck and Ryan Fraser return from injury. Leeds defender Liam Cooper is unavailable.
"Jack Hendry is a player that I liked when he was at Dundee," Clarke said. "I am probably a little bit surprised it didn't work out for him at Celtic if I am being honest.
"He showed a good maturity to move away and try to restart his career elsewhere.
"Sometimes the best way to have a look at a player if you can't see them live is to bring them into the squad."
Other than the revamped strikeforce, Clarke has largely stuck with the players who qualified for the European Championship finals.
That means no place for 21-year-old Celtic midfielder David Turnbull.
"He looks a good prospect for us," Clarke said. "Unfortunately for David, he is trying to get into what is probably the strongest area of the pitch. We have Ryan Fraser, Ryan Christie, Stuart Armstrong, John McGinn, all those attacking midfield players.
"I'm sure if David keeps up his current form, his chance won't be too far away."