By Chad Finn, Boston.com Columnist

Welcome to Volume 2, Edition 2 of Red Sox power rankings, a wide-ranging excuse to write about the best and worst performers of the previous month as a new one begins. The only rule of the power rankings is that there are no rules to the power rankings. Prospects, Lee Tinsley, media members, Bernie Carbo, front-office personnel - anyone is fair game. It's a measure of the exceptional and the unacceptable, with the middle ground unacknowledged. The top five are ranked; the bottom five are not since our pool of candidates is innumerable. Enough ballpark chatter. Let's get to it ...

TOP FIVE
1. Dustin Pedroia
Second to none
What more can you ask for? Pedroia has put up a .330/.411/.443 slash line so far this season as the No. 3 hitter for the second-best offense in baseball (5.19 runs per game, second only to the Tigers' 5.27). He hit all three of his homers and posted an .894 OPS in May. His defense is as stellar as it has ever been. And he's done it all with a thumb injury suffered on opening day that would have put lesser competitors on the shelf for a good chunk of the spring.

2.Clay Buchholz
True ace
This month's lesson: If you're the top starter on your ballclub and arguably in all of baseball this season, protecting your shoulder, elbow, and any other pitching-related hinges and appendages always must be in the front of your mind, even when you're catching a snooze with your child. Buchholz, tops on this list in April, gave Sox fans a scare when he had to have a start pushed back twice after feeling discomfort in his right AC joint in his shoulder, soreness that resulted, he said, from holding his napping toddler. No worries, though – Buchholz returned 11 days after his previous start to blank the Yankees on two hits through five innings Sunday, capping a month in which he went 2-0 with a 2.31 ERA in five starts.

3. Jarrod Saltalamacchia
Permanent contributor?
There are quite a few hitters we could list who were important in helping the Red Sox end May with a .500 record in the month (15-15) after a slow start in which they lost 9 of 11 games from May 3-14. David Ortiz was ferocious from beginning to end, and Daniel Nava, who has gone from an afterthought to an essential part of the lineup, had an .820 OPS in the month. But the nod here goes to Saltalamacchia, who put up an .825 OPS and drove 10 runs in 19 starts in May while superbackup David Ross was injured.

4. Craig Breslow
Steady southpaw
And why not offer a shout-out to an excellent and unsung performance on the pitching staff as well? Breslow, the veteran lefthander whose second most-similar pitcher all-time statistically is Hideki Okajima, has done excellent work out of the Red Sox bullpen this season, with a 1.29 ERA and .929 WHIP in 13 appearances. His return from an injury that cost him all of April came at the perfect time for the Red Sox, who suffered attrition when Joel Hanrahan was lost for the season and Andrew Bailey was on the disabled list.

5. Xander Bogaerts
It's all happening!
Jose Iglesias has had a heck of a run with the Red Sox so far this season, hitting .431 and playing the usual spectacular defense through two stints in the majors. But if there's a shortstop of the future to really be giddy about, look north toward Portland. Bogaerts, 20 years old and rated the eight-best prospect in the game by Baseball America before the season, is living up to the billing and then some, with 5 homers, a .306 batting average, and an .895 OPS so far for the Sea Dogs. One key sign of progress: he has one walk and 21 strikeouts in 97 Double-A plate appearances last season. This year, he's walked 30 times and whiffed 45 in 231 PAs.

BOTTOM FIVE
Ryan Dempster
Peaks and valleys
The 36-year-old righthander followed up a fine April (3.30 ERA, 43 strikeouts in 30 innings) with a not-so-fine May (5.54 ERA, 1.62 WHIP in six starts). The ups and downs are part of the package – in a dozen starts with the Rangers last year, six or seven were very good and three were brutal. But for the most part, he's been what the Red Sox thought they were getting – a durable innings-eater who will finish with an ERA in the mid-4.00 range.

Shane Victorino
Aches and pains
When he's played, Victorino has been a relatively pleasant surprise, particularly defensively, to those who thought he was in decline after a subpar 2012 season with the Phillies and Dodgers (.667 OPS). But that's the catch – when he's played. Victorino was limited to just 14 starts in May because of injuries, including a back problem that caused him to miss seven straight games from late April into the beginning of the month, as well as a hamstring injury that has kept him out since May 20.

Will Middlebrooks
Sophomore slump
One of the few real disappointments so far for the Red Sox this season, Middlebrooks is hitting just .201 with a .642 OPS in '13 after such a promising debut a year ago. In May, he hit .211 with two homers before winding up on the disabled list May 24 with a strained back.

Jacoby Ellsbury
Safe, then out
While Ellsbury didn't homer in May and put up a substandard .669 OPS, he did have his moments, including a five-steal game against the Phillies. Unfortunately, that's the last time he has played. Ellsbury suffered a groin strain on his club-record-setting fifth steal in the Sox' 9-2 win May 30, and hasn't been in the lineup since, missing a three-game set against the Yankees over the weekend.

Jonny Gomes
Power outage
Gomes has traditionally hammered lefthanded pitching over the course of his career (.504 slugging percentage, 53 homers in 931 at-bats). But he hasn't hit much of anything so far this season, putting up a .175/.323/.301 line against all pitchers. He hit .167 overall in May, and is hitting .158 against lefties, albeit with all three of his homers in 57 at-bats.

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