Martin Kaymer leads 2014 Grand Slam Challenge at 4 under par

With two majors -- and their eight combined rounds -- in the books, just 24 players have competed in every one of them. Bubba Watson, who missed the cut at the U.S. Open, isn't one of them.

Martin Kaymer, who won the U.S. Open at Pinehurst No. 2 with an impressive 9-under-par tally, leads in combined score halfway through majors season at 4 under par. Kaymer finished the Masters at 5-over-par 293.

In second place is Rickie Fowler at 3 under par. Fowler and Jimmy Walker are the only two players to post top-10 finishes in each of the first two majors of the year.

The last guy under par through the first eight major rounds of the year is Jordan Spieth, who finished at 5 under as co-runner-up at the Masters and 4 over par at the U.S. Open.

Here's the full major aggregate-score leaderboard: