Manager Lloyd McClendon is presiding over the most interesting Seattle Mariners team in a decade. / Drew Sellers, Sportspress Northwest

Among the first-half oddities for the Mariners: They fared far better against winning teams than losing ones. In compiling a record of 51-44, the Mariners went 25-14 (.641) against teams with a .500-or-better record (at the time they played) and 26-30 (.464) vs. clubs with a record below .500. To put finer point on it, the Mariners went 11-7 against first-place teams but 11-13 against last-place clubs.

That count omits the five losses the Mariners sustained during their season series with the lowly, but rising, Houston Astros, a team that recently moved into fourth place in the AL West due to the once-formidable Texas Rangers dropping eight in a row and 14 of 15.

Seattle GM Jack Zduriencik, who has roughly two weeks to make a deal or deals prior to the July 31 non-waiver trade deadline, is likely attempting to puzzle out exactly what kind of team he presides over, and whether it is in the franchise’s best interests to mess around this year with the team he’s built.

Zduriencik has to be encouraged that the Mariners hang with better teams, but flummoxed that they give away games to losing clubs. The Mariners are the only one of the five American League teams holding a playoff position that has a negative record against losing teams. None of the five National League teams in a playoff spot sport losing records against losing clubs.

To make Zduriencik’s decision to add a starting pitcher or a right-handed bat more complicated, the Mariners are 15-10 against AL clubs that would make the playoffs if they started today, including 7-6 vs. AL West-leading Oakland, 6-3 vs. the L.A. Angels and 2-1 vs. Central-leading Detroit (the Mariners have yet to play AL East leader Baltimore).

Add Seattle’s 2-0 interleague mark against NL East leader Atlanta, and the Mariners are 17-10 against teams occupying playoff spots. Their .629 winning percentage, in fact, ranks second among clubs that would be playoff teams if the season ended today. The 10 current playoff teams vs. each other:

Post All-Star break, the Mariners play 31 games against clubs that occupy playoff positions and 36 vs. clubs that don’t. Ten of the 31 are against the Angels with seven against the Athletics.

Leaps and bounds

Seattle’s 51-44 record represents an eight-game improvement over its standing at the halfway point of 2013 (43-52) and a 15-game upswing from 2012 (36-51). Behind the upswing:

• The Mariners went 27-18 on the road (.600), the No. 2 mark in the AL behind Detroit’s 28-16 (.636).

• Since April 23, when the Mariners snapped an eight-game losing streak with Kyle Seager’s three-run, walk-off homer against Houston, the Mariners are 44-31, the third-best winning percentage (.587) in the majors behind the Angels’ .635 and Oakland’s .613.

• The Mariners rank second in the AL with a 3.16 team ERA. That’s the lowest pre-All-Star break ERA in franchise history, eclipsing the mark of 3.25 in 2011.

• The Mariners have the lowest bullpen ERA in the majors at 2.39 and the lowest opponent batting average in the AL at .211.

• The Mariners bat .256 with runners in scoring position, a huge increase from their feeble .228 a year ago.

But . . . 

While the Mariners are 33-14 when they hit a home run, they are 18-30 when they don’t.

• The Mariners are 44-9 when they out-hit an opponent, but 6-32 when they are out-hit.

• While the Mariners have a winning record on the road (27-18), they are the only team among the 10 current playoff contenders  with a losing mark at home (24-26).

• The Mariners have 22 come-from-behind wins (sixth-most in the AL), but they also have 17 blown losses, including nine in an opponent’s final at-bat, making their margin for error virtually nil.

• The Mariners rank 11^th in the AL in runs (378), 14^th in hits (784), 14^th in walks (229), 14^th in batting average, 15^th in on-base percentage, 12^th in slugging and 15^th in OPS. This is not the batting profile of a team destined to reach the postseason, regardless of how good its pitching is. Since 1995, when the current playoff format was adopted, no team earned a wild card berth with an OPS of less than .773. Seattle sits at .677.

The following are American League wild card teams since 1995 with the lowest OPS numbers, and their league ranks. The Mariners are included for comparison purposes:

Add it up: As the second half starts, the Mariners are a bubble playoff team with intriguing possibilities if they reach the postseason. But if Zduriencik doesn’t made a deal for a starting pitcher, or a right-handed bat, or both, the Mariners will probably waste what is shaping up as their most interesting club in a decade.