a weak link (in the chain)

the weakest part of a system or the weakest member of a group of people that could cause the whole system or group to fail.

It's a strong team, though the goalkeeper may be a weak link because he's rather inexperienced.

The weak link in the chain is the computer software that controls the system.

• put the kibosh on something
• put the knife in
• put the lid on
• put the lid on something
• put the pedal to the metal
• put the record straight
• put the roses in cheeks
• put the roses in someone's cheeks
• put the screws on
• put the screws on someone
• put the seal on
• put the seal on something
• put the skids under
• put the skids under someone
• put the skids under something
• put the squeeze on
• put the squeeze on someone
• put the squeeze on something
• put the wind up
• put the wind up someone
• put thinking cap on
• put through
• put through hell
• put through hoops
• put through paces