Having battled through three qualifying matches to make it to the competition proper for the first time since 2021, Ymer carried his new-found form into the first set, after surviving break point in the previous game, he broke the Kazakh's serve in the fourth game to take a 3-1 lead.
The world number 175 was controlling his service games much better than Shevchenko was managing, and missed two set point chances in the eighth game, before wrapping up the first set 6-3 in the next game.
The second set was 3-3 in no time as both players were strong on serve, before the Kazakh was forced to save three break points in the next game. Just when Ymer looked to be getting on top, Shevchenko forced a loss of serve in game eight. However, the Swede was not perturbed, and broke back immediately to make it 5-4 to Shevchenko with Ymer to serve.
Both players held serve in their next games, but Ymer couldn't turn things around, as his 25-year-old opponent broke again to win the second set 7-5.
After a mammoth opening game in the third set, in which Ymer missed two break points, both players defended serve with ease, but again, Shevchenko stepped up his game when the opportunity to win the set presented itself - he converted his second set point in game 10 to take the set 6-4.
That disappointment looked to have taken the stuffing out of the Skara man, who lost his first serve of the fourth set. However, the heat seemed to be taking it's toll on the Swede - he needed a prolonged medical timeout having reportedly felt unwell on court.
Once play resumed, Ymer never looked at his best, and was soon 3-0 down despite forcing a break point in the following game, but would only win one more game in the match.
Shevhenko, who represented his native Russia until 2024, broke for a second time in the sixth game to give himself the chance to win the match. Ymer fought bravely and had a chance to break, but with his second match point, Shevchenko secured the win in four sets - 3-6, 7-5, 6-4, 6-1.
The world number 97 has progressed to the Second Round in Melbourne for the first time. American 25th seed Learner Tien awaits, while for Ymer, it's now one victory in 12 matches at Grand Slams - not including qualifiers - his win over David Sela in the First Round of the 2018 French Open.
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