XPath that selects grid cells excluding nested grids

I am constructing an XPath which selects cells in a grid, indexed by column and row. I have two types of grids in the application. One is a regular grid and another has nested grids (inside of its 's).

I want a single XPath which works for both grids.

(Yellow cell coloring indicates XPath selection)

Regular Grid:

XPath:
//*[@id='regularGrid']//table/tbody/tr[1]/td[1]

HTML:

<div id="regularGrid">
    <table>
        <tbody>
            <tr role="row">
                <td>Things</td>
                <td>Things</td>
            </tr>
            <tr></tr>
        </tbody>
    </table>
</div>

Nested Grid (Incorrectly selecting the nested TDs):

XPath:
//*[@id='gridWithNestedGrid']//table/tbody/tr[1]/td[1]

HTML:

<div id="gridWithNestedGrid">
<div class="k-grid-content">
    <table>
        <tbody>
            <tr class="k-master-row ng-scope" role="row">
                <td>1390</td>
                <td>1625</td>
                <td>625</td>
            </tr>
            <tr class="k-detail-row ng-scope" role="row">
                <td class="k-detail-cell">4167</td>
                <td class="k-detail-cell">486</td>
                <td class="k-detail-cell">6834</td>
            </tr>
            <tr></tr>
        </tbody>
    </table>
</div>

Problem: I need an XPath which works for both grids that doesn't select nested grids. The problem is that the nested grid div is nested inside of a div.

The following XPath works for the nested grid:

//*[@id='gridWithNestedGrid']/div/table/tbody/tr[1]/td[1]

But I need one that works for both.