Three To See, Rome: May 18

(1) Serena Williams vs. (Q) Simona Halep
Head-to-head: Williams leads 1-0

Record runs collide on the red clay. Serena roars into the semifinals riding a career-best 22-match winning streak, while Halep is on a personal-best six-match surge. On paper, this may look like a mismatch, but consider that Halep took a set from Serena in their lone meeting at the 2011 Wimbledon, and has taken down several Top 20 opponents playing the best tennis of her career this week.

"Usually players of that height don't serve as well—she has so much power on her serve, that's actually really awesome," Williams said after winning 12 of the final 15 games to beat Halep at Wimbledon.

The 21-year-old Romanian, already a veteran of three clay-court finals, knocked off Daniela Hantuchova in qualifying, surrendered just two games in a sweep of former French Open champion Svetlana Kuznetsova, edged fourth-seeded Agnieszka Radwanska, and defeated 13th-seeded Italian Robert Vinci, all before saving match points to fight off former Rome champion Jelena Jankovic on Friday.

Serena has played with more variety, using the slice serve wide on both sides effectively to set up her first strike, hitting the short-angled and deep backhand cross-court to set up her down-the-line backhand, and playing the drop shot to take advantage of opponents retreating into prevent-defense mode. If you’ve seen Halep play this week, you know she is tough and smart, but Serena has more power, more variety, and looks like she’s got plenty of motivation. This match is in her hands.

The Pick: S. Williams in two sets

(5) Rafael Nadal vs. (6) Tomas Berdych
Head-to-head: Nadal leads 13-3

The sight of Nadal on the opposite side of the net has been as ominous as a sink hole for Berdych, who is winless in four clay-court meetings with the Spaniard. Nadal lost the first set he ever played against Berdych on clay, but since then he’s rampaged in winning nine consecutive sets, including a 6-4, 7-5 triumph in the 2012 Rome quarterfinals.

Berdych stared down a similar bleak streak against world No. 1 Novak Djokovic on Friday. Carrying an ignominious 1-13 record against the 2011 Rome champion on court, Big Berd had dropped 11 in a row to the top seed before rallying for a 2-6, 7-5, 6-4 win. That should infuse Berdych with confidence, and consider that Robin Soderling, the only man to beat Rafa at Roland Garros, plays a similar, flat-hitting style.

Nadal saved 13 of 16 break points he faced in grinding out a 6-4, 4-6, 6-2 win over David Ferrer in two hours and 46 minutes. Ferrer does not hit as hard as Berdych, but he had some success attacking Nadal’s second serve and drawing the mid-court ball from the left-hander’s backhand. Berdych would be wise to try to club some returns and try to take charge of points off Nadal’s second serve; once the rally is neutral, Rafa’s court coverage, tremendous topspin and consistency give him the edge. Rafa looked vulnerable, at times, against Ernests Gulbis and Ferrer, but he's played crucial points with confidence and clarity and has had solutions for Berdych in the past.

The Pick: Nadal in three sets

(7) Sara Errani vs. (3) Victoria Azarenka
Head-to-head: Azarenka leads 5-1

Italian fans still celebrate then-world No. 26 Francesca Schiavone’s stunning upset of Serena Williams in the 2005 Rome tournament. Imagine the kind of impassioned revelry Errani will unleash among the Foro Italico faithful should she beat Azarenka to set up a possible final against Serena.

Two-time Australian Open champion Azarenka played a patchy quarterfinal against Samantha Stosur, surrendering seven straight games at one point, dumping eight double faults (including two doubles to donate serve), and finishing with more than twice as many errors (34) as winners (14). Vika does not change direction as well on dirt, she’s not always quick off the mark moving forward, and was victimized several times by Stosur’s drop shot.

Errani exudes the love of a good fight, can create angles off her topspin, will have a rousing Rome crowd behind her, and will pour every piece of herself into this match. Azarenka is nearly eight inches taller and has a substantial edge in power and reach against the 5’4” Italian. Look for her to attack the Errani backhand with deep, high drives to pin the Italian counter-puncher in her backhand corner, then flatten the forehand out cross-court to make Sara respond on the run.

Azarenka is still finding her feet on clay, but she’s 3-0 lifetime vs. Errani on the surface, including a 6-1, 6-2 win in Rome two years ago. If Errani can earn an early break, get the crowd into it, and get Vika thinking on second serve, it could be interesting, but Azarenka is the more accomplished player with more weapons and should advance.

The Pick: Azarenka in two sets