1977: Three year old season
Maruzensky started off the season with an open race held at Chukyo Racecourse with the intention of running in the Kisaragi Sho. However, other trainers feared losing to the undefeated horse, and avoided entering the race. The open race was almost canceled were it not for Masatoshi Hattori entering two of the horses under his training. Maruzensky ultimately won the race by a 2 and a half-length lead. After this win, however, Maruzensky fractured his shin, and was forced to take a three-month break.
Maruzensky returned to racing that May, and won another open race with a 7-length lead, but the horse was unable to enter the Tokyo Yushun (Japanese Derby) as horses brought over from abroad, including as fetuses at the time, were barred from running in a Triple Crown race. Nakanowatari reportedly begged to have the horse enter the race, pleading "Let [Maruzensky] enter the Japanese Derby. I don't care if the horse starts from the furthest outside. We won't interfere the other horses. We don't need the prize money. We just want to see how the horse would do". Hashimoto planned to go to court over this, but ultimately the decision was unchanged. Maruzensky being barred from entering the Derby caused controversy within the horse racing circle of Japan, with the official JRA magazine, Yushun, even holding a discussion panel on its September 1977 issue.
On June 26, Maruzensky was entered in to the Nihon Tampa Sho, where nearly 80,000 people attended to see the horse run. Maruzensky faced off the NHK Hai and future Kikka Sho winner Press Toko, but by far the most favored to win was Maruzensky, whose parimutuel odds were consistently at 1.0. At the race, Maruzensky quickly took the lead and had already gained a 6 to 7-length lead by the first corner. However, after passing the third corner the horse suddenly lost momentum and was almost passed by Inter Spencer. Maruzensky quickly regained the lead and ultimately finished the race with a 7-length lead. Nakanowatari later commented that "the track was bad that day, so I tried to run on the outside to keep the horse safe. Then Inter Spencer came up and the horse became aloof".
After this race, Maruzensky was moved to Hokkaido to run in a couple of races at Sapporo and Hakodate before running a race in autumn before the Arima Kinen. He was subsequently entered in to the Tankyori Stakes at Sapporo. Initially, there were plans of Tosho Boy running in that race alongside Maruzensky. However, that plan never materialized, and ultimately that race was run with only 5 runners. In the race, a filly named Yoshio Kazan took the lead and made Maruzensky run in 2nd within the pack, which was a first for the horse. However, Maruzensky gradually took over the lead and ultimately won the race with a record time of 1:10.1.
The horse was then moved to Hakodate. However, during training, Maruzensky had developed tendonitis, partly due to hitting the railings there. All of autumn was spent recovering from it, but symptoms began showing again when the horse was training for the Arima Kinen. While the tendonitis itself was relatively light, both Hashimoto and Hongo agreed to retire the horse as the only major races the horse could have entered by that time were the Arima Kinen and Takarazuka Kinen.
A retirement ceremony was held at Tokyo Racecourse on January 15, 1978.
