Like I said above - it can become a snowballing thing across consecutive windows. As with Arsenal - they build a decent squad around 2008 / 2009 and were on the verge of challenging for the title again. But they failed to build on it, then lost Hleb, then Adebayor, then Fabregas, Nasri, RVP and were right back to square one and fighting for fourth.
If you don't get the signings needed to push on this summer, it becomes harder to keep Coutinho next summer. He goes and suddenly Mane, Henderson and Clyne are having their heads turned and you are fighting to keep who you have rather than building.
That was largely the problem when Suarez left imo. Yes you lost a top player, but the problems really started when Rodgers failed to replace him with quality or build on the 2nd place finish. Then you had Sterling looking to leave and could only buy the likes of Balotelli, Ings and Benteke for the next couple of years.