Arsenal will be without influential winger Gabriel Martinelli, who sustained a foot injury last week.
David Raya is likely to return in goal after being ineligible to face his parent club Brentford at the weekend.
Takehiro Tomiyasu remains a long-term absentee.
Porto defender Wendell has recovered from a thigh issue suffered in the first leg, while Iran striker Mehdi Taremi might be fit after missing the home fixture in the tie.
MATCH FACTS
- Arsenal have won all three of their Champions League home games this season by an aggregate score of 12-0. They have never won four in a row at home without conceding in the competition.