Hamann said: "Last season we finished 37 points behind them in the league. This time we are 12 points behind with a game in hand. That shows we are closing the gap.
"In just one game there is not much of a gap between the sides, but over a season it is more difficult to keep in contact.
"Last season the gap was pretty big in the end but that is not the case this time around. We have a game in hand and they are 12 points clear of us,
"We have done okay against them. We only lost 1-0 in both league games last season and they were very close, and we have played them four times now in the Champions League and they haven't scored against us in those matches.
"We accept they won 4-1 at our place this season in the league, and we know we have a lot of work to do. They are ahead of us in the league for a reason, don't doubt that.
"We will see how things pan out. It will be good for the league if there is one team that can challenge Chelsea over the next few years because at the moment they are in a league of their own.
"Hopefully we will be that team. We are going in the right direction, we have shown that with our improvement from last season to this and we are heading the right way."