He will be difficult to replace when he leaves.

他离开后，他的位置很难有人接替。

《牛津词典》

But there are other aspects of his role that do not get as much attention and may be more difficult to replace.

但是对于他的角色，仍然存在许多我们不曾关注的方面，可能这才是最难以被取代的。

youdao

That can be a handy trade off, especially for lamps used in places where they are difficult to replace-eg, in chandeliers hanging from high ceilings.

这是一种简便的平衡，尤其对于那些安装在难以更换地方的灯泡——比如枝形吊灯里的灯泡。

youdao

Lee,however, would find it more difficult to replace his soldiers.

VOA: special.2009.10.15

But when scientists modify the mice with specific genetic tweaks, they are difficult to replace.

CNN: Rebuilding NYU's research labs after Superstorm Sandy

The five- or ten-year veteran invariably takes a certain amount of savvy with her that is difficult to replace.

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Mall owners predict that it wouldn't be difficult to replace Penney stores in the best U.S. malls, such as Aventura Mall in Aventura, Fla.

WSJ: Mall Landlords Get a Penney for Thoughts