Pool duel: Phelps leaves Lochte in his wake

>>> good evening once again from london where again tonight these games have made news. more than that they've made history and let's begin with fair warning . even though what happened here late today has been reported and replayed and repeated around the world already we try to supply an ample spoiler alert and this is one of those cases because we're about to report results. in gymnastics, a stunner of a gold medal performance for a young woman who is about to be the talk of our country. gabby douglas, who gutted it out and won on style and grit and poise and sheer talent at age 16, the first african-american ever to do so. and in swimming, this was the long-awaited showdown in the pool with the top two americans locking horns for a gold medal . nbc's kevin tibbles is across town in olympic park with all of it tonight. kevin , good evening.

>> reporter: brian , talk about a night of high drama in the pool. the final race of these games between the greatest olympic swimmer ever and the man who wants to dethrone him. this is it. and the crowd gathered early to see who would be victorious.

>> my heart says phelps . my head says lochte.

>> reporter: the final showdown between the most decorated olympic athlete ever and the teammate who has become his number one rival in the pool. round one saturday went to challenger ryan lochte , who left michael phelps in his wake in the 400-meter individual medley . shockingly, phelps finished fourth.

>> so far, these swimming games belong to ryan lochte .

>> reporter: olympic teammates since athens in 2004 , they worked together tuesday on yet another gold medal relay. in the 4 x 200 free style and winning phelps his historic 19th medal.

>> i was saying thank you for you guys making this possible.

>> reporter: tonight round two. the 200-meter individual medley . a race phelps owned at the 2004 and 2008 olympics. but a race lochte now holds the world record in.

>> i think there's a lot more riding on this now. this is really kind of the end of the match race and i think it's going to go down to the wire.

>> reporter: that's exactly what happened. in an electrifying finish the master michael phelps once again proved to the world he can still be number one. lochte took the silver in this, his last london race.

>> we've been racing for eight years now, and the rivalry that we've created has been tremendous for the sport. our friendship that we've created also is awesome.

>> i think once it's all over it's going to hit me emotionally.

>> reporter: tonight a new feather in phelps ' cap. the first man ever to three-peat gold in any swimming event. and there was more american olympic history made tonight when 16-year-old gabby douglas won the gold for the best all-around gymnast. the first african-american to win the title, her second gold medal of the games.

>> i'm going to seize the moment. it goes by so fast.

>> reporter: tonight the little dynamo with the mile wide smile is flying high and she's not done yet. she has two more events next week. and, brian , back to swimming, the phenom that is phelps isn't done yet either. he still has two more chances at gold here in london before he says he's going to hang up his swimming goggles for good. brian ?

>> kevin tibbles at olympic park across town, kevin , thanks. we