In your first example, Pineda started and pitched 4 innings. By rule, can't get the win. Perez came in in the 5th, and pitched 3.2 innings. Hildenberger and Harper combined for 1.1 innings to close a 9-3 win. Pretty easy to say Perez should get the win, he pitched the bulk of the relief effort. In the second example, Gibson was removed with 2 outs in the 5th, with a 6-3 lead, but had just walked two hitters to load the bases. Hildenberger got the final out in the 5th, preserving the 6-3 lead. Nobody else pitched more than an inning in a game that went to the 9th with the Twins leading 14-4. I'd say Hildenberger probably was the "most effective," and certainly had the highest leverage. In your third example, the Twins were up 15-0 in the bottom of the5th, when Berrios gave up four runs, and left with 2 on and 2 out. Duffy came on, suffered through dropped foul pop that should have ended the inning, but got the K. He then pitched a scoreless 6th, again surviving an error, with 2 more K's. Harper later pitched an inning, and Adams the final two innings of a game that ended 18-4. Hard to argue that Duffey wasn't the "most effective."