Small company, big employee

I am running a tiny IT company, which has a team leader and few developers. We did some projects for our clients in the past. We are working on our product now. I am frustrated now because the team leader lets the deadlines of our product (analysis, design, developement) passed easily. I cannot get what I want on time. It would be much cheaper and quicker if I outsourced the product to another company. The team response to our client’s request ontime though. I cannot simply let the team leader go because it is hard to find someone to replace him. I also have to depend on him to do maintenace and technical support to our existing projects. What can I do? Any advice is appreciated.