The first thing to know about is WHAT 5.1 analog output is and what it means...
If the player internally decodes all your surround it can then output that surround sound via HDMI or on analog audio outputs. Typically this looks like this on the back of your Blu-ray player...
You can see on the right, there are 6 RCA connectors which are the front L&R, the surround L&R, the center, and the subwoofer. That's 5.1 analog OUTPUT.
On the back of your A/V receiver you will have a similarly matching 5.1 analog input...
You can see, on the DVD input there are 6 RCA connectors labelled similarly for L&R main/surround audio with center and subwoofer.
So, 5.1 audio is connected from your Blu-ray/DVD player to the receiver using 6 analog audio RCA cables. Since almost any well made 75ohm cable will carry the audio fine, you just need 6 individual RCA cables.
Which means you need EITHER:
6 of these...
http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10236&cs_id=1023603&p_id=2680&seq=1&format=2
OR
3 of these...
http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10218&cs_id=1021803&p_id=2864&seq=1&format=2
OR
2 of these...
http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10235&cs_id=1023502&p_id=2769&seq=1&format=2
OR...
http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10235&cs_id=1023501&p_id=2773&seq=1&format=2
with one of the original RCA cables...
http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10236&cs_id=1023603&p_id=2680&seq=1&format=2
The bottom line is that you need a total of 6 individual RCA-ended cables to make an analog 5.1 audio connection which will carry HD audio.
Of course, if you have a 7.1 audio setup in your home, that means you will need a total of 8, not 6 RCA ended analog audio connections. Really, much easier than it may sound to you.