You are missing the point bro. They had Joe Cole, SWP and Duff as options and cover for the left flank alone. Yeah that can be seen as a little meh at first, but its far from that once you start listing out all the positions and the players competing for it. As you said earlier, its not about winning against a particular side but rather winning consistently against all the teams all season long. A league challenge is like a marathon, a long and slow race, the first most consistent runner reaching the finish line wins it. However, a team with 4 decent runners taking turns running at full capacity will finish the race much quicker against a team with a single or two exceptional runners. Basically, its all about quality of depth when it comes to challenging for the title. If Duff was losing form or gotten injured, they had the likes of Cole and SWP waiting to claim the position. Yes they're not world class but they are decent enough. That kind of quality in depth meant the competition for a place in the starting line up was  fierce and players worked harder to impress. The more players and the higher the quality of the player competing for the same position, the higher it is the the standard of performance, focus and commitment generated from the players. So massive was Mourinho's squad that he practically 2 or more world class and decent players competing for each position on the starting 11. No teams in the league at that time had that kind of quality in depth as Chelsea did. Jose was literally spoiled with choices with team selection and i actually feel  he didnt really need some of the those players he bought. He had the financial advantage, so why not buy players to deny his opponents the players they need to strengthen their  teams. To make matter worse, Chelsea spending spree inflated the transfer market and made it almost impossible for cash stricken team such as ours to pursue targets.   

A manager can only control certain things like  the trainings, team tactics and subs but there are certain thing beyond his control such as injuries and form. You cant really prevent those from happening but if it happens and it always does, the manager can only rely on the depth of his squad to deal and minimize the damage.

To give you an exact opposite scenario to Jose, recall our our team in the year Jose took over Chelsea. Ever wonder why Rafa didnt straight away purchase a 20 mill winger and were reluctant years after even tho we could actually afford it ? Its because the team and depth needed to be urgently improved. The lacked of depth was evident when Rafa took over, the test of managerial ability started almost immediately when the team was struck with an injury crisis. We practically had zero depth to cope with it. Rafa had to rely on the fresh inexperienced Academy graduates who lacked both abilities and mentality to perform at senior level. We simply didnt have the team and depth to compete in all competitions, the league was destined to be won by Chelsea as they steamrolled teams unscathed. We were probably at the level of the current Villa team, maybe slightly worse. But when Jose was having a headache selecting his first team from a massive reserve, Rafa was having a nightmare coping with the injuries and his managerial ability was tested to limit in working out tactics and shuffling his first 11 from a severely depleted team roster.

Against all odds, we managed to get to the Carling Cup Final only to lost the game for unlucky own goal. Thats ok because we went on winning the CL with a team that was nowhere near as complete and lethal as Chelsea. Despite their sudden and uninspiring success in football,  no one is going to remember that Chelsea team that. Because the year 2005 will always be remembered as the year a cracked Liverpool team marshaled by Rafa,  bulldozed their way through the CL, beating the likes Juventus and Chelsea, reaching the final and overcoming a 3 goal deficit in perhaps the greatest comeback in European football. In just one year Rafa had his managerial ability tested to the limit and he not only survived it but actually overcame with a bang! He transcended the Liverpool team and made us believing again. This is why i feel Rafa is the better manager because he has proven to be a very capable manager, he is cunning and fears no one, witty yet modest, respectful and diplomatic, calm in crisis and a brilliant problem solver. What kind of inspiring feat has Jose achieved that really puts him above Rafa ? Did he transcend the Chelsea team? Was he really the real reason why Chelsea won those titles ? Reckon most managers wont have problem winning the league.