Former Newcastle striker Tomasson coached Christensen in the Denmark national set-up before making the switch to Malmo in 2020.
And now the 45-year-old has heaped praise on 52-cap Denmark defender Christensen for having the tenacity and talent to make the grade at Stamford Bridge.
“Andreas Christensen is one of the best defenders around,” said Tomasson.
“It’s always good for the Scandinavian countries to have players coming across and making the grade in the Premier League.
“He’s had a great journey and has done tremendously well.
“The way he’s playing and the way he’s been playing here under the new manager, he’s been a great inspiration for a lot of Danish people.
“And not only the Danish people but also for a lot of Chelsea fans – he’s a top-class defender.”
Hailing the 25-year-old Christensen as a keen student of the game, Tomasson added: “The best players are thinkers, especially when it comes to choices.
“In top football you need to make choices, very quickly.
“So then you need intelligent players for sure.”
Reigning Swedish champions Malmo are pushing hard to retain their top-flight title.
Tomasson’s men have suffered a baptism of Champions League fire however, shipping seven goals in two-straight defeats to Juventus and Zenit.
With six games in 18 days in the offing, Wednesday’s west London visitors have little choice but to rotate their resources.
But Tomasson believes the experiences will bolster the club immeasurably for the future.
“The game tomorrow is important in a special way, because we have ambitions to show ourselves in the best way.
“What we’re experiencing here now is a masterclass in international football. And we want to develop as a club to gain a more international mindset, which is important.
“But at the same time we want to win the league in Sweden.
“We have a lot of games in a short space of time, so that’s why I will use the whole squad and I will be changing players tomorrow.
“We shouldn’t forget that we’ve come so far, winning the league last season.
“We want to do the impossible; be successful in Europe, but also do well in Sweden as well.
“This is two totally different football worlds playing each other tomorrow.”