It all depends on whether you can afford to drop Sanders or even have to drop Sanders. Also, it depends on what you need. Sanders is a blocking machine and will likely get picked up if you drop him. If you think that Dalembert or Lopez won't be picked up, I would say to keep Sanders b/c he will have a lot of time to recuperate during the all-star break. I'm unsure of the severity of Sanders' injury, but he is technically considered DTD and is awaiting a second opinion.
So, if you think Dal and/or Lopez won't get picked up, I'd keep Sanders. If you decide to pick one of them up, I would pick Dalembert b/c he is doing really well at the moment, but this could all change after the all-star break. Ultimately, it may be best to hold on to Sanders' through the all-star break and try to keep up to date on his injury status.