The USA international is playing against English opposition for the first time since agreeing to join the Blues in the summer transfer window for £57.6m.
He started the last-16 clash at Wembley and immediately caught the eye, forcing Hugo Lloris into a smart stop at his near post.
One Chelsea fan wrote on Twitter: “Pulisic playing well so far.”
“Omg I can’t wait for Pulisic at Chelsea next season,” a second said.
While a third added: “Pulisic x Sancho has Spurs spinning…needed at Chelsea asap.”
Pulisic is likely to be a regular starter for Chelsea due to doubts over Eden Hazard’s future and the decline in form of Willian and Pedro.
One Chelsea fan said: “Never quite understood caution Chelsea fans have regarding Pulisic, young players are always bound to be inconsistent likes of mbappe have clouded people’s judgement, Pulisic has impressed me more often than not whenever I see Dortmund play.”
A second said: “Fully confident Christian Pulisic will walk into Chelsea’s first team next season. A tier above Willian and Pedro currently.”
Opposition fans were quick to mock the Chelsea-bound ace, however.
An Arsenal supporter joked: “Pulisic has been s***.”
While a Liverpool fan wrote: “Pulisic is shocking, why on Earth would Chelsea pay 60m for him.”
Chelsea agreed to allow Pulisic to see out the rest of the season at Borussia Dortmund to help their bid to win the Bundesliga title.
After signing for the Blues, he said: “In summer I move on to Chelsea and to a new competition, the English Premier League.
“It’s a privilege to have signed for such a legendary club and I look forward to working hard towards being a contributor to their team of world class players.’
Chelsea director Marina Granovskaia added: “We are delighted to have signed one of Europe’s most sought-after young players.
“Christian has shown his quality during a fantastic spell in Germany and at just 20, we believe he has the potential to become an important Chelsea player for many years to come.
“We look forward to welcoming him to Stamford Bridge in the summer and wish him and Dortmund every success for the remainder of the season.”