Stielike's men just missed out on the Asian Cup title in January, as they lost the final 2-1 in extra time to host nation Australia.
With the Asian Football Confederation's (AFC) second round of qualifying for Russia 2018 set to begin on June 11, Stielike does not believe he needs to make major changes to his squad but maintains tweaks are required to make South Korea Asia's leading team.
The German coach has brought in six players for this week's friendlies against Uzbekistan and New Zealand, and all of them are under the age of 27.
Augsburg striker Ji Dong-won, Wigan midfielder Kim Bo-kyung and QPR defender Yoon Suk-young have been called up, along with K-League-based trio Kim Ki-hee, Lee Jae-sung and Kim Eun-seon.
"Players showed great performances as we ended up the Asian Cup in second place," Stielike said when announcing his squad.
"I didn't have to change the roster much. However, we need some of changes as well in order to develop ourselves to become first place, not second place."
Stielike is particularly interested in taking a look at Ji and Kim Bo-kyung, with both players having broken into their club's starting XI since the Asian Cup.
Ji has played nine straight games for Augsburg in the Bundesliga, while Kim has appeared in 11 consecutive Championship matches for Wigan, scoring twice.
"Kim Bo-kyung is almost a key player in Wigan; Ji Dong-won also played six matches out of seven matches as a starting member as he transferred to Augsburg from [Borussia] Dortmund," Stielike said.
"I called up two players in order to check their abilities by myself."
South Korea will play their first match since losing to Australia in Sydney, with a replay of their Asian Cup quarter-final against Uzbekistan in Daejeon.
The visitors will no doubt be keen for revenge after losing 2-0 after extra time to Stielike's side in the Asian Cup last-eight.
Son Heung-min scored twice in extra time to secure victory for South Korea in Melbourne.
