on/from the sidelines

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sideline /'saɪdlaɪn/ n. 球场边线;副业;局外人的观点

If you are on the sidelines or do something from the sidelines, you are not actively involved in something.

旁观;不参与

He has just stood on the sidelines up to now and let the situation get worse.

他仅仅是置身局外，任凭事态恶化。

She could only watch from the sidelines as her brother's health deteriorated.

她只能眼睁睁地看着弟弟的身体垮下去。