Wonderful OP..
When Klopp took over, even though we had just challenged for the title an year and a half ago then, it always seemed like he had massive task to do. Our team was bereft of attacking ideas, they were static and we obviously had defensive issues, which Rodgers tried to hide/mask under the Back 3, but he never really sought a long term fix for it.
It always frustrates me when people always refer to our 'defensive issues under Klopp', forgetting that he inherited them from Brendan Rodgers. Most of the individual mistakes the players have currently are from Brendan Rodgers' time. The uncertainty and the lack of communication that led to these errors and the soft center were all there.
Brendan Rodgers was a good attacking coach, but he lost his way and had too much to build again after we lost Suarez to Barcelona, Sturridge to injuries and Gerrard was at the tail end of his career. All these compounded his problems and he had to again fix the attack before he would look at the defense (not just by throwing money - which we did at times on Sakho and Lovren, but by also coaching the team for it - which we were unable to do sucessfully). In one way, yes we did adopt pressing under Rodgers, but our pressing was more uncoordinated under him. Our attack flourished by the movement he encouraged, but sometimes we did not even get players for the way he wanted us to play. This could even be attributed to the difference in ideologies between him and the famed 'Transfer Committee'. We still have the Committee, as do every other club in the world in different ways, but for us it now comprises of less members and it seems more coordination between the members before the request for a player is taken up to the owners. At that point, it seemed as if Brendan Rodgers had a lot to do to fix the team, but he also made a few mistakes along the way to the extent that it did not look like he would be able to fix the issues at any point of time.
What Klopp took over was a side with a lot of talent, but one that was extremely unbalanced. It had a lot of players who were not going to make it here (eg. Balotelli, Benteke, Ilori and Alberto), or who were past their peaks (Skrtel, Toure, Enrique, Lucas). The basics of attacking play was ingrained by Rodgers, but by then we had lost all the important players with whom they were incorporated and we no longer had players who could implement them. The pressing was uncoordinated. The defense was shambles with mistakes and lack of communication in them. The midfield has always been soft. Make no mistake, this was the side that Klopp inherited. One full of holes in every area of the pitch.
It has always been an interesting journey in observing how Klopp has approached to tackle these issues. What I liked most was that he didn't come in and straight away begin to start molding it to try and recreate his Dortmund side in terms of preference of systems and preference in profiles of players. He approached us as a completely different project. He gave our issues their own importance. He forgot about Dortmund (at least for the short term) and started using the tools in his hand. Klopp and his staff tried to train the players he had. He applied systems based on the players he had and adapted as per the availability of his players. He moved to 4-3-3 from his Dortmund 4-2-3-1, because our squad was built for that (again from Rodgers' time). A different coach may have stuck to his successful system and enforced the system on his players. Klopp prefers to wait to have his preferred resources before he can go his preferred ways. He also knew that he couldn't change too many things at once, it would be detrimental to his players.
Considering the above, he was sensible in not trying to tackle all these issues at once. We didn't and still don't have the money to throw at these issues straight away and see if they work, and then throw more money until it works. Some managers have worked their way to their successes by doing that. Others have had their resources to instantly get the players who can play their way. A few others have failed in trying to handle too many issues at once, ultimately deviating from their principles. Klopp was understanding enough to take on one issue at a time.
The first issue that he came on and looked was the uncoordinated pressing. Klopp's pressing is different. He coaches the team to press as a unit, analogous to the way Sarri coaches his team as a unit for the defensive line and it's as coordinated as one would like. Also, even if we did press before, counter-pressing was a different concept to our players. Simeone also gets his team to press, however his pressing is far away from Klopp's counter-pressing. This was the first issue he tackled and within his first season (it was just more than half a season in truth), we started pressing and counter-pressing more effectively. We had specific triggers which initiated the pressing at different moments of play and this was brought into the side by his training. He utilized players in Lallana and Firmino who were innately tuned towards pressing and let other players seek their leadership and triggers in pressing. We started to look a very good side when we demolished Chelsea and Man City and made all the way through to the Europa League final by beating some difficult opponents like Man United, Dortmund and Villareal before losing in the final. They were signs of what were to come. If only he could utilize players of the previous management for his style, how good would we be when he gets his preferred players for his way of play?
The second issue he sorted was movement up front. In Brendan Rodgers' last season, the loss of availability and form of players who were crucial in his best season resulted in our attack being static with lack of creativity. Klopp's counter-pressing helped as an additional playmaker, but he also utilized players who had good movement and gave them a suitable role. He started playing Firmino as the False 9 which created havoc in a lot of top sides. Of course, we had difficulty in beating some 'two banks of four' organizations, but the difference was notable. In subsequent transfer windows, he bought players who created/thrived in movement. This kept making us more and more dangerous and we're still improving. Now, our attack is one of the most potent in Premier League and I hope quite quickly enough, in Europe as well.
The third issue he was attempting to fix was linking midfield and attack. He solved this by using an available option and getting a new player. He pushed Lallana into midfield and bought Wijnaldum who are both adept at receiving the ball in tight spots and linking the midfield with the attack. With Henderson, Wijnaldum and Lallana, we were one of the most fluid midfields in the league last season and dominated a number of big sides. It was however broken up by injuries and Klop is now building a squad which is not reliant on specific players, but a set of players who can recreate his vision on the pitch.
While Klopp was looking and concentrating on these issues, the fourth issue escalated. This is our defense and GK situation. Our defense continued to make errors and this was highlighted by every man and his dog. But what was ignored is that, some defensive issues were already fixed before he even started fixing the defense. Our successful pressing has already reduced the need for large number of defensive actions in a game. We concede the second least number of shots per game. We had a similar record last season as well. The defense is suspect? Give less work to the defense. Not a revolutionary idea, but not a straight forward one in implementing as well. We did have a lot of clean-sheets in many games over last season and this, but specific games have haunted us where we have made successive mistakes. Now, we're on our way to ironing out those mistakes. We have a leader in defense and we have solid Full Backs as well in Clyne and Robertson and others who can clearly cover for them. This season he has also got our Full Backs deeper as cover and this has solved part of the problem as well. There is no doubt that we're getting better in this area as well.
In context, it is naive to talk about 'Klopp's defensive issues', when they were inherited and when he has clearly shown that he can coach a successful defense with his League Titles. Of course, he has a penchant for setting up attacking sides, but that Dortmund defense did not have half the issues he has been forced to tackle by the time he won Titles with them. I'm sure that will be the case in future with us as well. I'm more confident about us with him at helm than at any any point of time in the last couple of decades and he's creating a machine that does not depend on any particular player. It has been wonderful watching some of our moves in toying with the opposition, the dummies, back-heels, the movement, the creativity and not to mention, winning the ball high up - which is Klopp's favorite of the lot. It's going to be a proper ride and it's time we all got on it. Cheers to many many successful years full of trophies for Liverpool under Jurgen Klopp!