Substitutes made all the difference for South Korean men's under-23 football team in the 2-0 victory over the United Arab Emirates in Dubai on Monday, as they jolted a dull match back to life with their energy and pace.

To start the first of two test matches before the 2016 AFC U-23 Championship in Qatar -- also the Asian qualifying tournament for the 2016 Summer Olympics -- South Korea head coach Shin Tae-yong left most of his big guns on the bench. Shin later admitted it was by design, so he could test multiple lineup combinations and tinker with different formations before the Olympic qualifiers.

For the most part, the starters failed to pounce on their opportunity to make an impression, as they were unable to translate their superior ball possession into serious scoring chances.

Midfielder Kang Sang-woo's header in the 22nd minute that went off the opposing goalkeeper and then crossbar was as close as South Korea came to scoring in the opening half. The unit also suffered some defensive lapses and carelessly left some open space for the UAE attackers to exploit late in the first half.

Shin started the second half with six new players, since there was no usual limit of three substitutions, and they made an immediate impact.

Two of the substitutes, Park Yong-woo and Lee Seul-chan, nearly combined for an opening goal 12 minutes into the second half, though Lee's shot was off the mark.

Ironically enough, it was a starting winger Lee Yeong-jae who opened the scoring around the hour mark, converting a feed from Jin Seong-uk, the starting forward.

Both players were taken out of the match immediately after the goal, and the fresh bodies kept pushing the increasingly helpless UAE defense.

Hwang Hee-chan, a 19-year-old striker off the bench, rounded out the scoring late in the second half, with two other subs, Ryu Seung-woo and Kwon Chang-hoon, doing the dirty work on the right wing to set him up. Ryu, a member of the Bundesliga side Bayer Leverkusen, and Kwon, a rising star for the senior national team with a nose for the goal, are both expected to assume major offensive responsibilities once the AFC competition begins.

Against the UAE, the difference in qualities between the two South Korean units was so profound that it seemed as though South Korea played two separate matches.

Hwang, who'd flashed signs of brilliance in two friendly matches against Australia last October, played the hero for the subs, finally scoring his first U-23 goal in his third appearance.

The Austria-based teenager netted 11 goals in 17 matches while on loan to second-tier club FC Liefering in the first half of the current season. He has since returned to his original club FC Red Bull Salzburg, the reigning first-division champ, and he should continue his goal scoring ways with the national team.

"I scored a textbook goal, with Ryu Seung-woo and Kwon Chang-hoon making it all happen," Hwang said. "I didn't get good control of the ball when I received the cross. All of my teammates are playing well, and I am the only one that has to step up." (Yonhap)