I think to be honest it's disingenuous to draw parallels with the Alonso summer - this was during the time when money was being leeched out of the club for a start - but also because we were looking to replace someone who made our midfield tick. Teams are more likely to struggle when they lose a key midfielder - as we did when we lost Souness - because often they are responsible (in part at least) for the control teams have on a game. Alonso was to a large extent the metronome of the side, and unless we could have replaced him for an exact like for like player, it was always going to have an effect on all the players around him. Coupled to that was the fact we had a fairly awful transfer window during which he'd gone.
We've lost a top class player in Suarez, no question about that, but if you look through our history, we've lost top class attackers on two previous occasions that spring to mind (I'm not counting Torres because his head had gone for about a year before we sold him) - Keegan and Rush - and both times we ended up with better teams. The parallel to be worried about, if there is one, is the situation Spurs had last season. But then I'd argue that AVB had such a specific way of setting up his team, he needed to be able to completely cherry-pick the transfers to ensure the players were spot on for that system. If they'd spent the money on Hulk, Moutinho etc, then I think they'd have been in much better shape. But they had a DoF who was signing the players and clearly didn't get on with Villas Boas.
If Rodgers (and the coaching set up collectively) is smart - and I personally believe he is - then he would have been planning for Suarez leaving ever since last summer, and had a specific plan for how he wanted to shape the squad if Suarez left. We're not going to know that until a few weeks or a couple of months into the season. I don't necessarily think we need to replace Suarez with an equivalent forward - the comparison with signing Aldridge (not as good as Rush) and surrounding him with Barnes, Beardsley and Houghton (collectively brilliant) has been referenced before and I think it's a good one - but we need to make sure that the team becomes more effective in his absence; that we use this as an opportunity to step up rather than trying to fill a gap - which, to be honest, would end up with a slightly worse team, as the only players better than him are Messi and Ronaldo.
Strengthening the defence will make a huge difference. If Lovren provides leadership at the back, as well as being able to organise the four defenders and the pivot, that will benefit us hugely. Similarly, getting someone in at left back who is positionally good will make a big difference. I'll digress a little here, but I won't complain if we sign Bertrand. I haven't seen a great deal of him, but I don't get the impression he's awful, and he may well improve dramatically under Rodgers, which would be great to see.
I'll probably still be slightly nervous about our chances until we've filled the defensive positions, and I'd personally love us to sign an imposing central midfielder on top of that (Vidal would be lovely) but I'm far less in a tissy than I used to be in transfer windows because to be honest I have a huge amount of faith in our boss.