Depends on what that player actually brings to the team, and who his replacements are.
For example, when Denver traded Carmelo (and Billups) for marginal players the team improved.
And where did that get Denver? -- Nowhere.
Bottom line is they may go on a brief winning streak because they will be driven to show they can win without him. However, water always seeks its own level and the same will happen with this team. Talk about them being better without Rajon Rondo is beyond ludicrous.
Spoiler: Only 1 team can win. I know you are probably shocked.