Williams (left) and fly-half Ronan O'Gara are among the replacements
A couple of my mates have been asking me if I have set some sort of record for being on the bench in Lions Test matches.
There were the three in Australia in 2001 when I didn't get on, and the second two in New Zealand in 2005, where I came on for the final four minutes of the last Test and now I am on the bench for the first Test here in South Africa, so that's six out of seven now!
I would obviously like to start but there are 15 other guys not involved on Saturday, who have worked just as hard as I have on tour but haven't got the call.
It is all part of top-end sport - you learn to live with setbacks.
Nobody knew the team beforehand, it was the same policy as when they announced the original squad. 'Geech' [Ian McGeechan] just read the side out on Wednesday evening and then we went out for a big meal together to a steak house.
Obviously there were mixed feelings. Some boys were over the moon and some were disappointed.
If you are not disappointed, you shouldn't really be here because everyone wants that Test jersey. But after that initial feeling, the boys on the bench realise it is still a huge honour and massive privilege to be part of a Lions Test 22.
Funnily enough, I was sat next to Wally [David Wallace, who is starting at open-side flanker] at dinner on Wednesday night. We get on well and I have a huge amount of respect for him, he is a great player.
You have got to be professional and mature about these things. There are no personal grudges at all. We have been a tight group over the last few weeks and this was always going to be the big test as to how the boys reacted, but I think everyone has handled it brilliantly so far.
We had a really good, hard training session on Thursday with everyone helping the boys that are starting.
Some people assumed that because I wasn't involved in Tuesday's game against the Southern Kings that I would be in the Test side but I am too long in the tooth to ever assume anything in this game.
I knew that didn't necessarily guarantee me selection, although obviously there were boys in the party that travelled to Durban who knew they were definitely going to be in, but with the combinations and quality in the back row, I definitely didn't take anything for granted.
Even if you're not starting the game, you have got to prepare exactly as you would as if you were, because anything can happen in the first couple of minutes, as we saw on Tuesday when Euan Murray and James Hook both had to come off early on.
Williams was on the bench for the second and third Lions Tests in 2005
It is a difficult mindset on the bench. You are back and forth, warming up, trying to keep warm, but you have also got to watch the game.
I try to analyse it as much as you can and see what is going on because one minute you are sitting there and the next minute you are right in the middle of the battle.
You can't afford to let your mind wander and found yourself being part of the crowd. You have to be fully focused.
I think we are better prepared going into this first Test than we were four years ago in New Zealand. It is quite similar to how we were before the first Test in Australia in 2001 [which the Lions won 29-13 in Brisbane]. We were quite settled then but injuries knocked us back after that.
There have been one or two injuries here but we have coped with them and if you look at the squad for Saturday, it is very strong. Although they haven't played together as a 15, all the combinations are quite used to each other now.
We have had two games where we have blown the opposition away, against the Golden Lions and the Sharks, but the other games have been real dogfights.
But I think the way we have progressed in training, from where we were at Pennyhill Park five weeks ago, means we are all very happy with where we are at the moment.
People say perhaps we should have beaten some of the provincial sides by more but as I have said before, winning those tight games might have helped us more.
A Lions Test is different. When you are away from home, you never get the support like you do on a Lions tour. From the minute you walk out the hotel foyer and get on the bus, you are surrounded by fans, and hear the chants of "Lions, Lions".
That is a bit of a surreal feeling when you are away from home, whereas when you are in Cardiff, it's always manic.
There is a difference in intensity and expectation about a Lions Test and it is pretty emotional in the changing rooms.
Nine times out of 10 with your national side, you are with familiar people who you have played with a hell of a lot. You probably don't need to say so much because you know what they are thinking or feeling.
But when you are with the Lions, there are lots of different faces, and sometimes you have to check with the guy who is alongside you before you go out what he wants, and make those final little touches, but that is part of what makes the Lions special.
I am not one for head-butting walls to get myself going. I am normally pretty calm and quiet but as you get older you do get a bit more talkative and chirp up a little bit.
The guys on the bench will probably do a bit more talking beforehand because the ones who are starting will be really nervous.
We know how difficult it is going to be. You are never going to come to South Africa and under-estimate the Springboks, especially when they have one of their greatest ever sides at the moment.
It is a massive ask for us to beat them, but having been on a couple of Lions tours before, I don't think we could have asked to be in a much better position than we are.
Martyn Williams was talking to BBC Sport's Bryn Palmer