The phrase "donkey work" refers to tasks that are boring, repetitive, or require a lot of effort, much like the work that donkeys often do. It implies that the work is not very exciting or important. Full definition
Mours wingers do for them what Sanchez does for us, and even when mour was getting stick from some corners because they said Hazard was too good to be doing donkey work as he should be free to express. (justarsenal.com)
However, he wasn't doing much donkey work on the night as his two goals provided the Spanish giants with a lead to take into the second leg. (caughtoffside.com)
We tend to think of detachment as a symptom of our lackluster surroundings or uninspiring tasks, but boredom is actually more likely to be about your attitude than your environment (total donkey work obviously excepted). (inc.com)