As a once young stallion, Nadal was constantly put into the column of "could be."
Now 25, he's only a year older than Djokovic, but he's not a young 25 year old.
Counting the injury history and continued harsh physical game of Nadal's, I'd say it would be more than fair to give him the 28 deadline.
By the history of tennis, most players have declined steadily or rapidly after turning 28, you can count the legends but only Agassi and Laver had substantial success after turning 28 ( Federer has won one Slam and made two Finals since turning 28 himself ).
So are we now to condemn Nadal before his reign as a contender is over? Blasphemy, but to think he'll break any of Federer's records now is lunacy.
Let's look at it in groups from impossible, to improbable, to unlikely:
237 Consecutive Weeks as No. 1: Never gonna happen
29 Consecutive Grand Slam Quarterfinals: Nadal is currently 21 behind....
8 Consecutive Australia Open Semifinals: Nadal has back to back Quarterfinal exists
I could go on, but what's the point? Let's instead move on to the slightly more possible:
How many Slams will Nadal Finish With?
7 Consecutive Wimbledon Finals: Not counting Nadal's N/A in 09 he has made five in a row.
7 Consecutive U.S. Open Semifinals: Nadal sits at three.
5 Consecutive French Open Semifinals: Nadal made four before losing in the fourth round two years ago, he currently sits three away.
And then to shorten the time to get to the point, the big records people have been murmuring could fall, you know the ones, so how close is Nadal to those records really?
23 Grand Slam Finals:
Nadal sits at 13, just six shy of the previous record held by Lendl. Federer has struggled to make his usual Slam Final appearance and may only have a few left in him. Playing the conservative estimate that Federer finishes with 26 Finals when he's done ( three more than now ) that would mean Nadal has to make another 13 Slam Finals, or just over three years worth of Slams.
While possible purely on the fact of contention, Slam Finals are progressively harder to make than Slam Semis, examples would be McEnroe making three Slam Semis in his early 30s without a Final and Connors making seven Slam Semis without reaching a Final to the end of his career.
16 Grand Slam Titles:
Nadal is sitting at 10, but aside from his spectacular 2010 season, he's only won multiple Slams in one other year. Considering he's declined at the Aussie Open in the last two years one would think he may win three out of four just once more.
If we give him three more years that's 12 opportunities, of which he would have to score more than half the time to get that 17 titles. Djokovic doesn't seem to be going away and there is potential in rising stars. Also consider that we as fans have placed that French Open title as an almost given for Nadal and that may be soon coming to an end.
A 7th and record breaking title is all too possible but beyond that who knows and if Nadal isn't winning on Clay every year, how can we expect him do dominate at the other Slams? I still peg him to finish with 14.