That sort of injury for a prop, which is a position that relies so heavily on power and stability, could be seen as hugely damaging.
And especially for a player who had put his body on the line so many times for his club for so many years.
But four months on and the signs are very promising indeed.
So promising in fact, that the durable Waller, who holds the Premiership record for most consecutive games played, expects to be back in the not too distant future.
In fact, it could be the case that he only misses two Saints matches - the defeat at home to Saracens at the end of February and the 16-10 win at Worcester in March - due to Covid-19 having called a halt to rugby for so long.
“It’s good and it’s coming on really well,” said Waller when asked how his recovery process is going.
“I’m doing everything but running at the moment so that’s the next step.
“The surgeon said do nothing for the first two weeks so I took his advice and laid on the sofa for two weeks.
“There have been some challenges but I’m quite fortunate because I got a little gym setup here at home before lockdown because I could foresee the inevitable.
“I’ve been able to do my rehab and strength work and fitness work virtually on Zoom with the physios and strength and conditioning team.
“It’s been really good.
“It’s been interesting but for me on a personal note, sitting and missing a load of games is what really kills me mentally when I’m injured so at this point I’m not missing any games.
“I’ve got a routine where I can really focus, do my rehab every day and it’s probably helped me out a little bit to be honest.”
And when asked when he expects to return to action, Waller said: “It’s quite a wide-range of timeframes because everyone heals differently.
“The tendon itself can have a poor blood supply and take longer to heal but we’re ahead of schedule at the moment.
“It can be anywhere between five or six months to a year but we’re looking at the moment to be closer to the five-month period.
“That means I’ll probably be back around August, September time, which is probably when we’ll start playing again so that’s ideal for me really.”
Waller has been grateful for support from fellow professionals, and not just those at Saints.
“The surgeon I had is pretty world-renowned - I was quite fortunate to get in with him,” said the 30-year-old, who has made 280 appearances for Saints.
“He’s done a lot of operations on the lads - I think Anthony Watson had the same surgeon when he did the same injury as me. Ant’s back to full speed now.
“There have been a few boys who have done it who I’m in contact with.
“Lads from other clubs have been very forward in talking with me, especially one or two of the boys at Worcester.
“There’s another prop who’s done similar to me, he was seven weeks ahead of me, Conor Carey.
“He even sent a knee scooter down for me to get around on because he found that easier so he’s been a big help.
“I’m very confident and there’s life in this old dog yet. Don’t you worry about that!”
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