How to properly override salesforce standard object controller save method to intercept it in a visual force page

Hi there I created a visual force page to with a standard lead controller as the controller and extend it. I want to do this so i can still utilize the apex:detail control and not reinvent the wheel in dealing with the standard lead info, related list etc.

I added an apex:commandbutton and make it call save. When I click on this button I can clearly see that my function is being called. However, all changes that is done to the lead info via inline editing is not captured.

For example, If I edited LastName using the inline editing and i click on the apex:commandbutton the new LastName value is not being saved. It's almost like the save function that is being called by apex:commandbutton is not aware of the data changes.

the following is code to my visual force page.

<apex:page standardController="Lead" extensions="LeadTestExtensionController">
<apex:form >
    <apex:commandButton action="{!save}" value="Save" id="btnSave"/>
    <apex:detail subject="{!Lead.Id}" relatedList="true" showchatter="true" inlineEdit="true" />
</apex:form>
</apex:page>

the following is code to my controller
public with sharing class LeadTestExtensionController {
private Apexpages.StandardController controller;
private PageReference page;
private string id;
private final Lead myLead;
public String positions {get; set;}

public LeadTestExtensionController(ApexPages.StandardController stdController) {
    this.controller = stdController;
    this.myLead = (Lead)stdController.getrecord();
    this.page = ApexPages.currentPage();
    this.id = page.getParameters().get('id');
    List<Lead> myLeads = [select Opportunity_Stage__c from lead where id = :id];
    if(myLeads.size() > 0)
    {
        positions = myLeads[0].Opportunity_Stage__c;
    }
}

public PageReference save() {
    this.controller.save();
    PageReference newPage = New PageReference('/apex/RCS');
    newPage.getParameters().put('id',ApexPages.currentPage().getParameters().get('id'));
    newPage.setRedirect(true);
    return newPage;
 }

}

Once I click on the apex:command button, the page is being redirected to apex/RCS so i know its being called. However, if i return to the same lead, the last name doesn't change. I was under the impression that the following line would've called the standard controller's save function that should've taken care of the updating of the Last Name.

this.controller.save();

What am I doing wrong and how can I accomplish this. The above code is heavily simplified version of my actual code. What I am trying to do in my actual code is to check the value of certain field and if it meets certain criteria I want it to do something. However, I can't seems to see the new value entered.

Thank you.