The Germany centre-half looked shaky at times and the Dortmund backline allowed Shakhtar substitute Douglas Costa too much space to bring down a long ball and make it 2-1 midway through the second half.
However, Hummels headed home a corner three minutes from time to placate his manager who felt the German champions deserved at least a point.
"There were episodes in the game when Mats could have done better but...he got back into the game to equalise," Klopp said.
"I am happy with the result. We withstood the pressure inside the stadium but conceded two silly goals. I don't know if we played our best but it may be a part of tactics not to show all your strengths.
"Statistics says we had 18 shots while Shakhtar had eight. If you do not win, you have to score goals at least. We managed to do that and created a good basis for the return game," he added ahead of the second leg in Dortmund on March 5.
The match went ahead despite at least five people being killed when an internal plane carrying fans to the match in eastern Ukraine overshot the Donetsk runway and broke up as it attempted an emergency landing in the fog hours before kick-off.
"It is a terrible tragedy, we were told about that in the corridor while heading for the pitch. We express our condolences to the families of the people who were killed in the plane crash," Klopp added.
Shakhtar coach Mircea Lucescu half blamed the Ukrainian season's current three-month mid-season break for his team's failure to twice hang on to a lead after Darijo Srna scored the opener with a free kick, only for Robert Lewandowski to level.
"We still have to learn how to defend a result in the closing stages of the game," he complained.