There is an extension called OpenHere that will do this. It will add the option in the right click context menu
Open in This Window. Just right clcik on the link you want to open in the same tab.
Edit in response to comment:
You can do it with AutoHotkey. You have need to download it and install it on your PC. After that just copy the code below and save it with a
#IfWinActive, - Google Chrome$
Now when you press Alt + LClick, it will copy the link to the clipboard and past it in the address bar of Chrome. Just press the button and click and release with the click and the link will open in the same tab.