Jeonbuk Hyundai Motors had just taken a 1-0 lead over FC Seoul in the 75th minute of their K League 1 season opener Saturday.

Naturally, two minutes later, Jeonbuk's starting goalkeeper Song Bum-keun was replaced.

So, what happened there?

Jeonbuk head coach Kim Sang-sik sent in a 19-year-old goalkeeper Kim Jeong-hoon to tend the net for the final stretch. Fortunately for Jeonbuk, nothing disastrous happened in the teenager's K League debut, and Mo Barrow scored a late insurance goal to seal a 2-0 victory.

Coach Kim made that unusual move to take advantage of new substitution rules, aimed at encouraging teams to use under-22 (U-22) players more often but is already being exploited by teams.

Starting this season, K League 1 clubs are allowed to make up to five substitutions, up from three, if they start at least one U-22 player and if their 18-man roster includes at least two U-22 players.

One twist: If only one U-22 player gets the start, then another U-22 player must enter the match as a substitute in order for clubs to be permitted five substitutions. If not, clubs will be limited to three substitutions.

In that Jeonbuk match, coach Kim had started one U-22 player, Lee Sung-yoon but used up his three substitutions. Then midfielder Han Kyo-won suffered an injury in the 77th minute and needed to be replaced. To be able to use extra substitutions, Kim had to bring one extra U-22 player off the bench. And he called Kim Jeong-hoon's number, while also replacing Han with Choi Chul-soon. The coach ended up using his maximum five substitutions.

While the league may have good intentions, as far as giving youngsters a chance to compete on the big stage, teams may already be taking advantage of rules in ways that defeat the whole purpose.

In that same season-opening match, Lee Sung-yoon, 20, got the start for Jeonbuk but was lifted just 23 minutes in.

Also on Saturday, Suwon FC put two U-22 players into their starting lineup, Cho Sang-jun and Lee Gi-hyuk, but they were replaced after only 16 minutes.

The following day, Incheon United did the similar thing, starting a pair of U-22 players, Park Chang-hwan and Kim Chae-woon, only to substitute them for veterans 21 minutes later.

After all, there's no clause that stipulates how long U-22 players must stay on the field if they start. And clubs would be opposed to the league controlling those minutes anyway.

The pattern is obvious: Teams will start two U-22 players even when they know those players won't necessarily impact the match, just so that they can meet the quota and make five substitutions for the match.

For both Suwon FC and Incheon United, substitutes quickly made their presence felt.

Kim Seung-joon, in for Cho, drew a penalty that Yang Dong-hyen converted in the 28th minute for Suwon's first goal. They ended in a 1-1 draw against Daegu FC.

Elias Aguilar, who replaced Park Chang-hwan, scored Incheon's lone goal in their 2-1 loss to Pohang Steelers.

Having seen other clubs toy with the substitution rules, Gangwon FC head coach Kim Byung-soo said on Monday that he wasn't a fan.

"These rules are complicated, and I don't understand why they're applied that way," Kim said before Gangwon's match against Ulsan Hyundai FC. "Is it right to replace two young players after just 15 minutes? Will that really help develop young players? I don't think so." (Yonhap)