The former Real Madrid man has voiced his admiration for his team-mate following his impressive display in the win over Bayern Munich
The former Shakhtar Donetsk star received heavy criticism after he missed a number of gilt-edged chances in the Champions League win over Real Madrid in midweek, but silenced his critics with a goal and an all-round impressive display in the 3-0 win at the Allianz Arena on Saturday.
Sahin believes the pressure on Mkhitaryan's shoulders this season has affected him at times but insists the 25-year-old can become a great player at Dortmund.
"There aren't many players in the world with his quality, the way he turns and accelerates. When he gets it right, nobody can stop him, and he proved that against Bayern," Sahin told the official Bundesliga website.
"I'm not worried about him at all. He's having a very good season with a good return of goals and assists.
"Obviously he was disappointed to have missed those chances against Real but he's a really important player for us and I rate him highly.
"He's a player who wears his heart on his sleeve. He's in a country he doesn't know and there's a lot of pressure on him."
Mkhitaryan has netted seven goals in 27 Bundesliga appearances so far this term.