Noted Japanese matchmaker Joe Koizumi, in his report posted on fightnews.com, described 4the bout as "such a close affair that there were arguments for and against the verdict."
Judges Anek Hongtongkam of Thailand scored 114-113 and Ukrid Sarasas of Japan saw the bout at 115-113, both for Yamaguchi, while Alex Vidal of the Philippines penned it 115-112 for Santillan.
Koizumi believed Yamaguchi’s relentless attack in the last round was the turning point of his victory as the score was tied at 104-104 on the scorecard of Hongtongkam after the 11th round.
"Yamaguchi, in the final canto, displayed his last surge and gained an important point on the neutral referee Hongtongkam’s tally (which had been 104-104 after the 11th)," said Koizumi.
Santillan floored Yamaguchi with a solid left shot with the Japanese barely withstanding the Filipino’s fiery assault later.
Yamaguchi fought aggressively in the last round on the way to the close victory, his 15th straight in 16 fights that include a draw and 11 wins by knockout. The WBC- ranked No.11 welterweight Santillan dropped to 22-3-1 with 16KOs.
This is the third time Santillan lost the OPBF 147-pound crown he seized by conquering Korean Suk-Hyun Yun via split decision on Jan. 26, 2001 at the Waterfront-Cebu City Hotel.
After two successful defenses, the 28-year-old Santillan was dethroned by Japanese Hiroshi Watanabe by split verdict in their rematch on Oct. 14, 2002 at the Park Arena in Komaki, Japan.
Santillan regained it by defeating Watanabe also by split decision in their third encounter, but was knocked out by Japanese Kazuhiko Hidaka in the fourth round on March 19 last year in Tokyo.
Santillan reclaimed the OPBF championship fromHidaka in their return bout Dec. 3 last year, only to hand it over to Yamaguchi the other day.