Tsendbaatar Erdenebat (Mongolia) needed a strong final round in order to stay in the hunt in his second Olympic appearance. The 2016 Olympic quarterfinalist edged Nick Okoth (Kenya) via split decision, in a fight where scores were all over the place. 

Okoth won on two of the cards by scores of 30-27 and 29-28, while Erdenebat won 30-27, 29-28 and 29-28. Every round was split 3-2, with judges Diarmuid Macdiaramada (Ireland) and Alejandro Barrinetos (Cuba) disagreeing on every round. 

Judge Karn Naklam was the only judge of the five who had the fight even through two rounds (19-19), scoring the third and final round in favor of Erdenebat.

The bout was as competitive as the scores suggested. Okoth came in as the oldest male participant at age 38, fighting 13 years after exiting in the opening round of the 2008 Beijing Olympics. The Kenyan served as the aggressor throughout the fight, picking up steam as the bout progressed to where he was dialed in with his right hand. 

Erdenebat was the cleaner boxer, his style proving to be the more preferred when all was said and done. 

van Duong Nguyen (Vietnam) couldn't sway the judges in the opening round  despite scoring a knockdown, but managed to do enough damage to eventually get past Tayfur Aliyev (Azerbaijan). Nguyen won a split decision, earning scores of 29-27, 29-28 and 29-28 to overrule scores of 29-28 and 29-28 in favor of Aliyev. 

A clean opening round of boxing by Aliyev was nearly ruined after suffering a knockdown late in the frame. Aliyev still won the round 10-9 on four of the five scorecards, but lost all momentum as Nguyen kept coming forward for the balance of the fight. 

Erdenebat and Nguyen will meet in the next round.

Alexy Miguel de la Cruz (Dominican Republic) had his way with Keevin Allicock (Guyana), dominating every round en route to a lopsided unanimous decision victory. Scores were 30-27, 29-28, 29-28, 29-28 and 29-27 in favor of de la Cruz, who will next face number-two seed Albert Batyrgaziev (ROC) on Wednesday.

Mirco Cuello (Argentina) and Hamsat Shadalov (Germany) didn't make it easy on the judges, with Cuello eventually prevailing by split decision. The five judges were all over the place, with none of the rounds scored unanimous.

Cuello won by scores of 30-27, 30-27 and 29-28 to overrule matching 29-28 scorecards in favor of Shadalov in a fight that featured plenty of action and momentum shifts. In the end, it was Cuello's cleaner punching that allowed him to advance to Round of 16 on Wednesday, July 28.

With a nickname like "The Scouse Lomachenko," Peter McGrail never had a chance to live up to the billing.

The Liverpool southpaw was ousted from competition following a three-round points loss to three-time Olympian Chatchee-Decha Butdee (Thailand). Scores were 30-27, 30-27, 29-28, 29-28 and 29-28 in favor of Butdee, who is competing in his third weight division in as many Olympics. 

The 36-year-old Thai southpaw spent the entire fight countering McGrail, connecting with straight lefts and utilizing the ring as McGrail struggled to land clean shots. Butdee now advances to the Round of 16, as was the case in 2016 before losing a controversial decision to Vladimir Nikitin as a bantamweight.

Daniyal Shahbakhsh (Iran) advances to the Round of 16 following a thorough three-round decision win over Mohamed Hamout (Morocco). Scores were 30-27, 30-27, 29-28, 29-28 and 29-28 in favor of Shahbakhsh, who will next face two-time Olympic Bronze medalist Lazaro Alvarez (Cuba) on Wednesday, July 28.

Butdee and Cuello will meet in the Round of 16 on Wednesday, July 28.

Ceiber David Avila (Colombia) has so far kept pace with his performance in Rio 2016, advancing to the second round of Tokyo 2020 following a three-round unanimous decision over Mohamad Alwadi (Jordan).

Avila won by scores of 30-27 (4x) and 30-26. He will next face Everisto Mulenga (Zambia) in the Round of 16 on Wednesday, July 28. Avila made it that far for Colombia as a flyweight in 2016 before being eliminated. 

Jean Carlos Caicedo (Ecuador) prevailed by split decision over Mykola Butsenko (Ukraine) in perhaps the first upset of 2020 Olympic competition. Caicedo won by scores of 29-28 on three cards, overriding two judges who had same score but in favor of Butsenko.

Caicedo swept the opening round, while all five judges had Butsenko claiming round two. The third and final round was split, though in favor of Caicedo who at one point quit boxing to become a beer delivery driver. 

Caicedo was persuaded by the 2016 Ecuador Olympic boxing team—including his cousin, Carlos Mina who fought as a light heavyweight—to return to the sport and embark on a path to compete in Tokyo 2020. The 26-year-old now advances to the Round of 16 where he will next face Samuel Takyi (Ghana) on Wednesday, July 28.

Serik Temirzhanov (Kazakhstan) lodged a lopsided unanimous decision win over Roland Galos (Hungary). Scores were 30-25, 30-25, 30-27, 30-27 and 30-27, all in favor of Temizhanov who was credited with standing eight counts in rounds one and two. 

Temirzhanov will next face Duke Ragan (USA), who claimed a split decision win over Samuel Kistohurry (France).

Ireland's Kurt Anthony Walker fought through a mid-fight surge from Spain's Jose Quiles and a late round cut to advance in featherweight competition. Walker won by scores of 30-27, 29-28, 29-28, 29-28 and 29-28 to move on to the Round of 16.

Walker jumped out to a strong start, winning the opening round on four of the five scorecards. Quiles took control of the action in round two, pulling even on four of the five scorecards while trailing 20-18 on the dissenting card. 

The final round determined the fight, with Walker overcome a cut over his right eye, boxing wisely to take the round and the fight. He will next face France's Mirazizbek Mirzakhalilov, the number-one seed and a heavy favorite to win Olympic gold. 

Jake Donovan is a senior writer for BoxingScene.com. Twitter: @JakeNDaBox