The home side are bidding to win this competition for the third since 2012, while the visitors have never lifted this trophy in their history.
Match preview
Sitting down in third position in the K League 1 standings after seven matches, Hong Myung-bo will certainly not be satisfied with his team's early-season form.
Sixteen goals have come from those fixtures - three more than any other team - but it has taken two dominant wins in their last two outings to get back on track.
Nevertheless, Hong and his squad have reached the business end of this competition by losing just two of their 10 fixtures, both of which came in the group stages.
Ulsan only edged through to the last 16 by one point through the best-ranked second-placed teams, but they have since defeated Ventforet Kofu and fellow South Korean side Jeonbuk Hyundai Motors.
The Tigers had been behind in the latter of those ties, only to ultimately come through with a 2-1 aggregate success to keep their hopes of a third trophy alive.
Meanwhile, Yokohama F Marinos have endured an indifferent start to the J1 League campaign, only collecting 14 points from their opening eight matches.
Harry Kewell was placed in charge at the turn of the year and he has since delivered seven wins and three draws from his 12 matches in charge.
In this competition, victories over Bangkok United and Shandong Taishan have been posted in the knockout rounds, Yokohama requiring extra time to overcome the former 3-2 on aggregate.
Kewell will be encouraged that the Tricolor have put together a run of just one defeat in eight games, yet they failed to overcome Shonan Bellmare last time out when holding a 2-1 lead with their opponents at a player disadvantage.
Ulsan Hyundai AFC Champions League form:
W
D
W
W
D
W
Yokohama F Marinos AFC Champions League form:
L
W
D
W
W
W
Team News
With Ulsan having scored four times in the opening 61 minutes against Gangwon FC on Saturday, Hong was able to rest several of his players during the closing stages.
That could subsequently lead to an unchanged team, even if that sees their top goalscorer in this competition - Martin Adam with five strikes - start on the substitutes' bench.
Joo Min-kyu netted twice in the previous game and should retain his spot, but another veteran in winger Lee Chung-yong is expected to remain among the replacements.
Katsuya Nagato will miss out for Yokohama courtesy of collecting two yellow cards during the second leg of the quarter-final.
Changes could be made after the last game with Ryo Miyaichi and Anderson Lopes both pushing for recalls to the attack, although Kento Shiogai did score his first goal of the season in the preceding fixture.
Ulsan Hyundai possible starting lineup:
Jo; Seol, Lim, Kim, Lee M; Ko, Lee D; Um, Lee K, Ludwigson; Joo
Yokohama F Marinos possible starting lineup:
Popp; Matsubara, Kamijima, Watanabe, Kato; Nam, Sakakibara, Uenaka; Mizunuma, Shiogai, Koike
We say: Ulsan Hyundai 1-1 Yokohama F Marinos
With a second leg to come, it would come as a surprise if either team were particularly gung-ho in this match. With that in mind, do not be surprised to see a low-scoring draw play out at the Ulsan Munsu Football Stadium.