The in-form Colombian international striker is clearly crucial to the Scottish champions’ hopes of overcoming Bundesliga giants Borussia Dortmund and reaching the last 16 of the tournament for a third consecutive season.
But Morelos is carrying the threat of a suspension into the tie as a consequence of the two bookings he collected during the group stage - at home to Lyon on matchday one in September and away to Brondby on matchday four in November.
With qualification for the knockout phase assured with a game to spare, Morelos was rested for Rangers’ final group stage game in Lyon in December to avoid the risk of a yellow card which would have seen him banned for the first leg of the tie against Dortmund.
Morelos, who has scored nine goals in his last 11 games for Rangers, has been a talismanic figure on the European stage for the Ibrox club. He is their all-time leading scorer in European competition with 27 goals so far.
Fashion Sakala is the only other Rangers player on the verge of a suspension, the Zambian forward having also been booked twice during their group stage campaign.
Dortmund will be without suspended influential midfielder Emre Can on Thursday night but have no players on the bookings threshold for the second leg.